Marc Leman
email: marc.leman@ugent.be

Musical gestures and embodied cognition

In this keynote, musical gestures will be discussed in relation to the basic concepts of the embodied music cognition paradigm. Video examples are given of studies and applications that are based on these concepts. 1

INTRODUCTION

Interactive music systems have both a technological and experiential component. The technological component is concerned with the tools that translate human movements into manipulations of sounds. The experiential component is concerned with the intended control of the tools, which is accomplished through gestures. In this keynote, we mainly focus on the later component, as we believe that a good understanding of it is a prerequisite for a successful tool development.

Recently, the foundations of musical gestures have been reconsidered, and new viewpoints have been inspired by the insights from research on embodied music cognition (Godøy and Leman, 2011). The goal of the keynote is, firstly, to clarify the concept of musical gestures in relation to the basic concepts of embodied music cognition, secondly, to consider a number of implications for technology development (Leman, 2007). To illustrate that point, a number of video excerpts will be shown and discussed.

I should add here that in the paradigm of embodied music cognition, it is assumed that cognition is more than just mental processing and its corresponding brain activations. Indeed, music cognition is considered to be situated (i.e. embedded in an environment), and enacted (i.e. put into practice through action) (see [START_REF] Varela | The Embodied Mind: Cognitive Science and Human Experience[END_REF][START_REF] References Barsalou | Grounded cognition[END_REF]. The embodiment hypothesis refers to an action-oriented basis for making sense of our environment. In that context, we consider the former focus on music and mind within in a broader perspective that puts emphasis on embodiment, action, and consequently, gestures.

BASIC CONCEPTS OF MUSICAL EMBODIMENT

The paradigm of embodied music cognition is based on a number of concepts, related to: (i) the body as mediator, (ii) the gesture/action repertoire, (iii) the actionperception coupling, and (iv) the link with subjective experiences, such as intentions, expressions, empathy, and emotions. Let me introduce these concepts and discuss how musical gestures are related to them.

Body as mediator

The body of a person can be considered as the mediator between the person's environment and the person's subjective experience of that environment. This viewpoint is widely known (e.g. [START_REF] Merleau-Ponty | Phénoméńologie de la perception[END_REF], but it always needs a careful explanation. Indeed, the role of the body is particular in that it causally connects with a physical environment as well as with an experience (of the subject who owns that body). The physical environment can be described in an objective way (e.g. the waveform of the music on my sound recorder). The experience can only be described in a subjective way (my subjective feeling in response to the music on my sound recorder). Similarly, musical gestures can be described in an objective way as movement of body parts, but they have an important experiential component that is related to intentions, goals, and expressions.

The action/gesture repertoire

When the body acts as a mediator between our environment and the experience, it will build up a repertoire of gestures and gesture/action consequences. Such a repertoire is called a gesture/action-oriented ontology. It is the set of commands and their perceived outcomes that is somehow kept in memory and used for the next action and the interpretation of the next perceptions.

The repertoire is based on the idea that humans interact with the environment on the basis of actions, that is, movements that are made to achieve a particular goal, such as access to resources, or access to other persons. The repertoire can also be considered as the reservoir of experiences. This repertoire thus comprises connections between commands, sensations of the external world through our senses (exterioception), but also sensations of our body movements (proprioception) and of our body state (interioception). Musical gestures form the core component of this repertoire.

Gestures

Interestingly, the concept of musical gesture applies both to sounds as well as to body movements (Godøy & Leman, 2010). For example, in a study on guqin performance [START_REF] Henbing | A gesture-based typology of sliding-tones in guqin music[END_REF], it was possible to show that sonic gestures (identified in music) reflect sound-producing gestures (hand movements), and that these gestures can be understood as concatenations of more elementary gestural components. The rules for combining elements of this alphabet are defined by natural constraints (i.e. physical, physiological limitations) as well as cultural constraints (preferred movements). More recently, [START_REF] Desmet | A statistical analysis framework for assessing a clarinet player's performer gestures in relation to locally intended musical targets[END_REF] studied clarinet playing gestures in relation to musical intentionality and expressiveness. [START_REF] Leman | Basic gestures as spatiotemporal reference frames for repetitive dance/music patterns in Samba and Charleston[END_REF] studied Samba dance from the viewpoint of spatiotemporal representations.

Entrainment

The research on entrainment considers how resonant systems adapt their synchronization with each other. Traditionally, this work has a more exclusively focus on timing aspects in relation to synchronization, such as the tempo and phase during synchronization tasks in music playing or dancing.

Gestures and entrainment

In several more recent studies conducted at IPEM, we consider the idea that gestures may condition entrainment, and therefore, that the focus of entrainment should be broadened to include a spatiotemporal dimension that is rooted in bodily gestures. Such an approach may lead to a gestural topology of point clouds, a concept that has been introduced by Naveda and Leman (2010) and further developed in Maes et al. (submitted). Typically, with gross motor gestures that subsume a particular repetitive choreography, there is a large spatial region where the body part can be at a particular point in time, which ensures tolerance for synchronization variability, and therefore some flexibility in entrainment.

In contrast with these gross motor gestures, fine motor gestures require a more precise spatiotemporal deployment. This happens when people interact with a music instrument. In that case, there is less tolerance for synchronization variability, and less flexibility in entrainment. Just consider the fact that rehearsals of music ensembles often aim at getting the synchronization right.

The coupling of action and perception

From the previous paragraph it is clear that the gesture/action repertoire forms part o f a m o r e c o m p l e x mechanism that controls the interaction between environment and subjective experience. This mechanism, also called, the action-perception coupling system, or the action-perception engine, is responsible for prediction and, as we will see, also for issues that involve musical intentions (musical action-goals).

Understanding the components and the dynamics of the action-perception coupling system is a hot research topic in modern cognitive science (see [START_REF] Wolpert | Principles of sensorimotor learning[END_REF]. In general terms, it makes sense to consider at least two mechanisms for learning, which I call the sensorimotor loop and the action-perception loop. The sensorimotor loop is a low-level loop where the motor activity is basically driven by sensory input from the environment. In contrast, the action-perception loop is a high-level loop that involves the gesture/action repertoire. The two loops are not exclusive and they can run in parallel. For example, in producing a sound on the clarinet, the sensorimotor loop can maintain the control of the mouth and breath in relation to the sound production, while the action-perception loop can use the repertoire of learned fingering patterns (that have been practiced earlier) as a global controller for the expressive production of the sound. As such, the assumption is that action and perception are controlled by an actionperception coupling system involving different loops.

Interestingly, the prediction principle also works the other way around. When a person perceives a certain sound, the person may rely on previously learned action-outcome knowledge in order to assume the action for the sound. The latter principle is indeed fundamental in our approach because it explains why interaction is embodied. This principle, which is comparable to a Bayesian inference in statistics, also offers a key to modeling our multimodal (sound-gesture) interaction with music. Typically, when an every-day sound is heard, the person will tend to act in relation to how that sound is produced. In contrast, when an abstract sound is heard, the person will tend to act in relation to particular parameters of the sound that can be reproduced by movements (such as general contours).

Musical intentionality, expressiveness, and empathy

Our research at IPEM has contributed to the idea that music may establish an intentional layer of communication between listener and player. This intentional layer provides access to the (assumed) goals of the music. It is based on an action-perception coupling system that tends to use actions as causes of perceived patterns, thus turning perceived sound patterns into action patterns that could have caused the perceived sounds. This mechanism forms the basis of a number of social phe-nomena of music, ranging from empathy to social bonding.

THE ROLE OF TOOLS

Finally a word should be said about tools. Tools are of outmost interest to us for two reasons. Firstly, with tools, we can study the characteristics of the actionperception coupling system. For example, during piano playing, the action-perception coupling can be disturbed by using a headphone that introduces an auditory delay. In order to be able to cope with the music playing, the agent may have to change the usual strategy for predicting the consequences of his actions. The change of strategy may reveal the mechanisms that underlay the coupling system. Secondly, with tools, we can build new applications that intervene with the action-perception coupling system. One example is DJogger [START_REF] Moens | D-Jogger: Syncing Music with Walking[END_REF] that extracts the tempo of your walking and provides music at the same tempo of the walking tempo. Humans tend to entrain and thus walk in phase with the musical pulse. Typically, they minimize the prediction error of the walking pulse until it fits with the musical pulse. IPEM has developed tools for different domains such as music education, therapy or entertainment. During this keynote, several examples will be given and further discussed

CONCLUSION

The paradigm of embodied music cognition provides an interesting viewpoint on musical gestures. It assumes that music is based on a tight relationship between sounds and experiences that are mediated by the body. Apart from the research that aims at understanding this phenomenon, the goal is to be able to control the nature of this complex phenomenon, and apply this control in applications for music education, health, art and other domains.

The paradigm of embodied music cognition provides an approach of how to deal with the experiential component in interactive music systems. The research field is likely to become an important partner of technologydriven music research.

This text is a modified version of a chapter that will appear in the book M. Lesaffre and M. Leman (eds.), "The power of music -researching musical experiences", Leuven: ACCO

, 2012.

Actes des Journées d'Informatique Musicale(JIM 2012), Mons, Belgique, 9-11 mai 2012


Carlos Dominguez-Carrió
email: carlosdominguezcarrio@gmail.com

Anna Sanchez-Vidal

Claude Estournel

Guillem Corbera

Joan Lluís Riera

Covadonga Orejas

Miquel Canals

Josep-Maria Gili

Seafloor litter sorting in different domains of Cap de Creus continental shelf and submarine canyon (NW Mediterranean Sea)

Keywords: plastics, funneling, litter hotspots, longlines, cold-water corals, continental margin

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The widespread distribution of materials produced by human societies that get stranded ashore or reach the seabed is now considered a critical issue in terms of marine conservation [START_REF] Galgani | Global Distribution, Composition and Abundance of Marine Litter[END_REF][START_REF] Rangel-Buitrago | Curbing the inexorable rising in marine litter: An overview[END_REF]. Its presence in all parts of the ocean has alerted national and international authorities, researchers and stakeholders worldwide, which foresee the consequences of not properly addressing this issue in the forthcoming years (UNEP, 2009;[START_REF] Agamuthu | Marine debris: A review of impacts and global initiatives[END_REF]. The vast majority of discarded items are primarily made of plastic or have plastic components [START_REF] Jambeck | Plastic waste inputs from land into the ocean[END_REF][START_REF] Beaumont | Global ecological, social and economic impacts of marine plastic[END_REF], mainly due to its low manufacturing cost and its durability. This property also makes plastic extremely dangerous, since it can last for decades once discarded [START_REF] Laist | Overview of the biological effects of lost and discarded plastic debris in the marine environment[END_REF]. After plastic items have reached the marine environment, measures to retrieve them are complex and expensive, especially with increasing depths [START_REF] Iñiguez | Marine debris occurrence and treatment: A review[END_REF]. Besides the aesthetic, health and economic problems derived from the accumulation of human-derived objects in the marine environment, litter is steadily becoming a serious threat to wildlife, since it can kill or harm all sorts of marine organisms, from algae to birds [START_REF] Kühn | Deleterious effects of litter on marine life[END_REF]. The list of deleterious effects caused over marine fauna is extensive, and includes among others the entanglement or smothering of sessile animals [START_REF] Yoshikawa | Entanglement of monofilament fishing lines and coral death[END_REF] and the ingestion of fragmented litter by heterotrophic organisms (e.g. [START_REF] Courtene-Jones | Consistent microplastic ingestion by deep-sea invertebrates over the last four decades (1976-2015), a study from the North East Atlantic[END_REF]. Recent studies have documented the ingestion of microplastics by commercially important deep-sea species [START_REF] Carreras-Colom | Spatial occurrence and effects of microplastic ingestion on the deep-water shrimp Aristeus antennatus[END_REF][START_REF] Cau | Microplastics in the crustaceans Nephrops norvegicus and Aristeus antennatus: Flagship species for deep-sea environments?[END_REF], indicating the great implications that its accumulation may have for the marine ecosystem and also for human health.

In European seas, around 30% of all marine litter that accumulates on shelf, slope and canyon habitats can be attributed to abandoned, lost, or discarded fishing gear (ALDFG; Pham et al., 2014b), although this percentage can reach 50-80% in traditional fishing grounds, such as Campania, Sicily or Liguria [START_REF] Angiolillo | Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy)[END_REF][START_REF] Consoli | Marine litter in an EBSA (Ecologically or Biologically Significant Area) of the central Mediterranean Sea: Abundance, composition, impact on benthic species and basis for monitoring entanglement[END_REF]Enrichetti et al., 2020). These high percentages may be explained by the increase of the fishing effort during the past decades and a steady transition to synthetic and more durable materials to manufacture fishing nets and lines [START_REF] Gilman | Abandoned, lost and discarded gillnets and trammel nets[END_REF], which lead to an increased likelihood of gear loss [START_REF] Richardson | Estimates of fishing gear loss rates at a global scale: A literature review and meta-analysis[END_REF]. The remaining litter items observed over the seabed derive from a wide range of sources, yet most of them consist partially or entirely of plastic (Pham et al., 2014b;[START_REF] García-Rivera | Spatial and temporal trends of marine litter in the Spanish Mediterranean seafloor[END_REF]. It is now becoming very common to find plastic bottles, plastic bags and clothes half buried in the sediment or entangled around rocks in deep water environments [START_REF] Van Den Beld | Marine litter in submarine canyons of the Bay of Biscay[END_REF][START_REF] Moriarty | Spatial and temporal analysis of litter in the Celtic Sea from Groundfish Survey data: Lessons for monitoring[END_REF]. In the Mediterranean Sea, studies performed over the continental margin have found litter items in almost all surveyed sites [START_REF] Angiolillo | Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy)[END_REF][START_REF] Pasquini | Seabed litter composition, distribution and sources in the Northern and Central Adriatic Sea (Mediterranean)[END_REF][START_REF] García-Rivera | Spatial and temporal trends of marine litter in the Spanish Mediterranean seafloor[END_REF][START_REF] Gerigny | Seafloor litter from the continental shelf and canyons in French Mediterranean Water: Distribution, typologies and trends[END_REF]Enrichetti et al., 2020). Highest densities are generally registered in areas close to shore or immediately adjacent to large cities [START_REF] Strafella | Assessment of seabed litter in the Northern and Central Adriatic Sea (Mediterranean) over six years[END_REF][START_REF] Buhl-Mortensen | Marine litter in the Nordic Seas: Distribution composition and abundance[END_REF], with accumulatio (" h ") b b hy h h inside submarine canyons or following the path of the main oceanic currents [START_REF] Tubau | Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes[END_REF]2015;[START_REF] Cau | Dumping to the abyss: single-use marine litter invading bathyal plains of the Sardinian margin (Tyrrhenian Sea)[END_REF][START_REF] Pierdomenico | Massive benthic litter funnelled to deep sea by flash-flood generated hyperpycnal flows[END_REF].

Aiming to minimize the effects produced by human-derived objects in the marine environment, the European Commission included marine litter in the Marine Strategy Framework Directive (MSFD) as one of the 11 descriptors to b wh h h 'G E ' (GE ) of European seas (Council of the European Union, 2008). The MSFD provides the legal framework to encourage Member States to report and subsequently monitor the abundance of marine litter in their territorial waters, leading to the implementation of area-specific management measures to reduce the amount of litter that reaches the marine environment, and designing specific actions to minimize land-based sources when possible [START_REF] Galgani | Marine litter within the European Marine Strategy Framework Directive[END_REF]. The application of such measures, however, must be based upon a comprehensive knowledge of the actual composition, abundance and spatial distribution of marine litter in each area.

The continental shelf and the submarine canyon off Cap de Creus currently belong to a Site of Community Importance (SCI) of the Natura 2000 Network (BOE, 2014). Following the demands of the MSFD, the implementation of an ecosystem-based approach to manage human activities in Cap de Creus marine area requires a thorough evaluation of the amount of litter items that can be found in its shelf and canyon habitats. Making use of 68 underwater video dives performed between 80 and 1570 m depth prior to the declaration of the SCI, this paper aims to (1) evaluate the quantity and spatial distribution of marine litter on the Cap de Creus continental shelf and submarine canyon,

(2) identify the main causes of such distribution, and (3) assess the potential impacts of ALDFG over the three main cold-water coral species dwelling in the submarine canyon, namely Madrepora oculata, Lophelia pertusa and Dendrophyllia cornigera.

Materials and methods

Study area

The Gulf of Lion forms a prograding continental margin characterized by a rather wide continental shelf (up to 70 km) and a complex network of submarine canyons incising its continental slope and shelf, which play a prominent role in the hydrological and sediment dynamics of the whole margin [START_REF] Canals | The Role of Canyons on Strata Formation[END_REF]. The Rhône River supplies most of the terrigenous input h w h h 6.5 rticulate matter discharged every year [START_REF] Poulier | Combining flux monitoring and data reconstruction to establish annual budgets of suspended particulate matter, mercury and PCB in the Rhône River from Lake Geneva to the Mediterranean Sea[END_REF]. Most of the sediment remains stored on the shelf until specific atmospheric situations trigger highenergy oceanographic events such as dense shelf water cascading and sea storms that are able to resuspend and transport large quantities of sediment, organic matter and pollutants to the deep, mainly along submarine canyons [START_REF] Canals | Flushing submarine canyons[END_REF][START_REF] Palanques | Suspended sediment fluxes and transport processes in the Gulf of Lion submarine canyons. The role of storms and dense water cascading[END_REF][START_REF] Salvadó | The role of dense shelf water cascading in the transfer of organochlorine compounds to open marine waters[END_REF][START_REF] Salvadó | Transfer of lipid molecules and polycyclic aromatic hydrocarbons to open marine waters by dense water cascading events[END_REF].

Cap de Creus Canyon is located at the southernmost end of the Gulf of Lion shelf. The canyon head is just 4 km ahead of Cap de Creus promontory and is deeply incised on the continental shelf at 125 m depth (Figure 1; [START_REF] Lastras | A walk down the Cap de Creus canyon, Northwestern Mediterranean Sea: Recent processes inferred from morphology and sediment bedforms[END_REF]. Because of its location at the southern exit of the dominant circulation pattern in the Gulf of Lion, and also because of the obstacle effect of the promontory that deviates offshore coastal and shelf currents, Cap de Creus Canyon behaves as the preferential conduit of water and sediment h ' h h p margin and basin [START_REF] Canals | Flushing submarine canyons[END_REF][START_REF] Palanques | Suspended sediment fluxes and transport processes in the Gulf of Lion submarine canyons. The role of storms and dense water cascading[END_REF]. The presence of strong bottom currents and the supply of large quantities of organic material favors the development of rich benthic communities, both on the continental shelf and the submarine canyon [START_REF] Dominguez-Carrió | ROV-based ecological study and management proposals for the offshore Marine Protected Area of Cap de Creus[END_REF], where dense patches of cold-water corals, mainly Madrepora oculata, have been observed [START_REF] Orejas | Cold-water corals in the Cap de Creus canyon, northwestern Mediterranean: spatial distribution, density and anthropogenic impact[END_REF].

Most of Cap de Creus peninsula was declared a maritime-terrestrial Natural Park in 1998, including a narrow shallow water peripheral belt of the innermost continental shelf (mostly infralittoral stage) (BOE, 1998)

Video surveys and imagery analysis

The extensive dataset used in this study was obtained from 68 underwater dive is provided in Table 1, with reference to the video platform used. Data obtained during the PROMARES cruise (dives 37 to 44) was partly published in [START_REF] Tubau | Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes[END_REF], and considered in this study given its relevance to better determine spatial patterns in litter distribution along Cap de Creus submarine canyon.

All underwater dives were performed from the mid and outer continental shelf (80-90 m water depth) down to the submarine canyon floor at 1600 m (Figure 1; Table 1). Dive length was extremely variable (from 80 m to 3 km) and dependent on weather conditions, underwater visibility and bottom current speed. The total seafloor distance covered was 47.5 km, which represents an area visually examined of about 7.5 ha. All transects were performed as straight as possible while keeping a constant speed above ground of 0.3 m•s -1 in average.

Final Cut Pro 7 (Apple Inc.) video editing software was used to remove the time intervals when the underwater vehicle stayed stationary, so multiple counting of the same item was avoided. Those sections with poor image quality, mostly due to sediment resuspension or excessive distance from the seabed, were also identified and subsequently removed from the statistical analyses. During the PROMARES cruise (dives 37-49), an average field of view (FOV) estimated at 3 m was selected for litter quantification (see details in [START_REF] Tubau | Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes[END_REF]. Dives performed with the manned submersible JAGO (dives 1-9 and 32-36) had an estimated average FOV of 2 m. For the remaining transects, which were performed with smaller ROVs that filmed from a closer distance to the seabed, a 50 cm average FOV was chosen to calculate litter density. All human-derived items and cold-water coral colonies of the species Madrepora oculata, Lophelia pertusa (recently reclassified as Desmophyllum pertusum, see [START_REF] Addamo | Merging scleractinian genera: the overwhelming genetic similarity between solitary Desmophyllum and colonial Lophelia[END_REF] and Dendrophyllia cornigera were identified and annotated within the selected field of view in each underwater dive.

Data treatment

Marine litter items were classified in two main categories: (1) ALDFG, which included bottom trawl nets, bottom trawl cables, longlines and trammel nets, and (2) urban litter, which was further subdivided in plastic, metal, glass, ceramics, clothing (regardless of its fabric), paper and wood. It should be noted that all fishing gears and related items, whether made of plastic or metal, were all attributed to ALDFG. Making use of transect length (L) and width (W), densities for each litter category were calculated at the transect level as items per ha -1 , simply dividing the number of items by the area explored in each dive (De = items / L • W).

To account for spatial and depth variability in the distribution of litter items, five domains were defined within the study area in and around Cap de Creus Canyon (Figure 1), following those defined by [START_REF] Lastras | A walk down the Cap de Creus canyon, Northwestern Mediterranean Sea: Recent processes inferred from morphology and sediment bedforms[END_REF]:

1. Northern mid and outer shelf (NS): the continental shelf north of the eastern tip of the cape, from 80 to 150 m depth.

2. Southern mid and outer shelf (SS): the continental shelf south of the eastern tip of the cape, also from 80 to 150 m depth 3. Canyon head (CH): from the shelf break at a mean depth of 150 m down to 400 m depth inside the canyon.

4. Upper canyon (UC): between 400 and 1000 m depth.

Middle canyon (MC)

: between 1000 and 1600 m depth.

The impact of ALDFG on the above-mentioned cold-water coral species was assessed by calculating the percentage of entangled colonies of each species along selected underwater dives (1-9) carried out in the canyon head, from 160 to 390 m depth.

Modelling the bottom currents

The free surface, generalized sigma vertical coordinate, 3D hydrodynamic model SYMPHONIE described by Marsaleix et al. (2006[START_REF] Marsaleix | Energy conservation issues in sigma-coordinate freesurface ocean models[END_REF]Marsaleix et al. ( , 2012) )

Results

Composition of marine litter

In total, 833 litter items were identified in the video images recorded on the continental shelf and submarine canyon off Cap de Creus. This corresponds to an average density of 110 items ha -1 for the entire study area (80-1600 m depth). The number of items and density per dive, organized in the different litter categories, is provided in the Supplementary Table 1.

There were 394 urban litter items (47% of the total), which appeared in 30%

of the dives (Table 1). A wide variety of objects could be identified, including

Spatial and depth distribution

Mid and outer continental shelf. Urban litter items were not commonly observed on the videos registered on the continental shelf, with only 14 items annotated in 1.93 ha explored. This represents an average density of 7.2 items ha -1 for the continental shelf, with recorded densities slightly higher on the northern side (Figure 3), although no clear pattern could be determined (Figure 4a). Plastic objects and objects with plastic components constituted around 38% of all reported urban litter (5 items), with densities below 4 items ha -1 on both shelves. Glass was the second most common category, with 4 items (30%). Litter objects made of other materials, like metal (8%), ceramics (15%) and textiles (15%), appeared in lower numbers, and no items made of wood and paper were reported. Densities of ALDFG were similar on both sides of the continental shelf (Figure 3), with slightly higher densities on the southern (59.5 items ha -1 ) than on the northern side (45.6 items ha -1 ). Most ALDFG items were registered along the 100 m isobath north and east of the easternmost part of the cape (Figure 4b), where rocky outcrops and mixed substrates were generally observed in the images. Longlines were by far the most common type of ALDFG found on the continental shelf, accounting for 76% of all fishing-related items. With 79 longlines reported (NS: 33; SS: 46), densities on both sides stayed around 40 items ha -1 (Figure 3). Trammel nets appeared only on the southern side (12% of ALDFG, 10.5 items ha -1 ), generally entangled over small and medium sized rocks (Figure 2k). Bottom trawl nets and cables represented 13% of all ALDFG, with most nets appearing on the southern shelf (NS: 3; SS: 10), where their density was around 8.7 items ha -1 (Figure 3, examples in Figure 2i,j)

Canyon head. 28 urban litter items were identified on the 1.33 ha explored, corresponding to a density of 21.1 items ha -1 (Figure 3). Per material types, 51% of urban items were made of metal (11.3 items ha -1 ) and 24% of plastic (5.3 items ha -1 ). The number of glass and clothing items was almost negligible. Most of the amphorae observed in the footage (4) were reported in the canyon head. ALDFG reached maximum values in this domain (323 items), with a density of 243.6 items ha -1 (Figure 3). All but 3 dives performed in the canyon head contained remains of ALDFG, with some dives reaching local densities above 500 items ha -1 , particularly on the westernmost part of the canyon head (Figure 4b). More than 80% of all ALDFG identified corresponded to longlines (290 items), which represents a density of 218.7 lines ha -1 (Figure 3, examples in Figure 2g,h). It should be noted that according to the tradition in the area and the design of longlines and trammel nets, these two techniques are not practiced in areas deeper than 400 m.

Parts of bottom trawl nets also reached here the highest numbers of any domain (33 trawl nets and ropes, 24.9 items ha -1 ), and were mostly observed as thick pulling ropes, especially in dive 42.

Upper canyon. Urban litter items were much more abundant in the upper canyon than in the previous two domains combined, with 122 items identified in the 3 ha explored, resulting in a density of 39.5 items ha -1 (Figure 3). Most objects were made or had plastic components (76%, 30.1 items ha -1 ), with a smaller fraction made of metal items (18%, 7.1 items ha -1 ). Other materials were represented by objects made of wood, ceramics, glass and paper, all of them with densities lower than 1 item ha -1 . The abundance of ALDFG decreased significantly below 400 m depth, with only 7 fishing-derived items identified in the upper canyon (2.3 items ha -1 ; Figure 3). All ALDFG in this depth range had a bottom-trawl origin, with most items being actual trawl nets

(5) and pulling ropes (2) (Figure 5a).

Middle canyon.

With 230 objects identified in the 1.2 ha explored, the highest number of urban litter items of any domain corresponded to the middle canyon (187.8 items ha -1 ; Figure 3). This represents 58.4% of urban litter items identified in the whole video footage. The largest fraction corresponded to items made of plastic, a material appearing in almost 90% of the urban items reported in this domain. In contrast, metal objects accounted for only 6% (11.4 items ha -1 ), whilst the remaining categories contributed with less than 1-3% each (Figure 3). In some specific areas at around 1200 m depth (Dive 40), there existed accumulations of several litter objects in a build-up wh b " h " wh aged items were observed half buried under the sediment (example in Figure 5b). Regarding ALDFG, 2 longlines and 3 bottom trawl nets were identified in the middle canyon, where an overall density of 4.1 items ha -1 was reported (Figure 3). It should be noted that bottom trawling is not usually practiced in Cap de Creus at depths below 800 m.

Bottom currents

Bottom current speed and direction averaged for the month of February 2012 after applying a bilinear interpolation to the modelled data (gridded at 700x700 This would indicate that the results shown here could be underestimating the maximum current speeds that can be reached during cascading events.

Interaction of litter with cold-water corals and other sessile fauna

A total of 335 colonies of cold-water corals were identified in the canyon head, of which 302 Madrepora oculata, 26 Dendrophyllia cornigera and 7 Lophelia pertusa. Besides some variability at transect level, and independently of the species, more than 10% of the colonies had on average entangled longlines around them (Table 2). In most cases, longlines were observed hooked around the branches of the cold-water corals, regardless of the species (Figure 7). In general, most corals seemed to remain alive when having cables twisted around them. However, the distance of the camera to the colonies did not allow for a closer examination to determine the percentage of polyps affected and the level of harm produced. It was also impossible to determine how many broken branches resulted from the interaction between longlines and the coral colonies.

Some of the thickest longlines were also observed to act as substrate for several sessile species to live on, although for some of them precise identification was certainly difficult. Most species were bushy hydrozoans and bryozoans, together with the abundant polychaete Sabella pavonina, which was commonly observed attached to lines suspended over the seafloor (Figure 7c). Besides the effects produced by longlines on cold-water corals, other fishing gears were also observed to interact with benthic and demersal fauna. As an example, a large trammel net was found fully extended over the soft bottoms of the southern continental shelf (Dive 34; Figure 2l). As observed in the images, this net had at least two large spiny lobsters (Palinurus elephas) caught in it, one of which still alive, as well as other dead fishes impossible to identify. Also on the southern shelf, a large bottom trawl net was found lying over a sand plain with small outcropping rocks (Dive 36;

Figure 2i). This trawl net was covered by a large number of small organisms (several species of sponges, ophiuroids and holothurians), indicating that it might have been lost for some years. Inside the submarine canyon, litter hotspots were generally observed over soft-bottom areas (Figure 5). Although the level of interaction was not quantified, the presence of these deposits seemed to overlap with the distribution of burrowing megafauna, including the anemone Cerianthus membranaceus (Figure 5a).

Discussion

Seafloor litter provenance, abundance and distribution

The popularity of Cap de Creus as a touristic attraction, with a significant increase in tourism and recreational boating during summer months (Lloret et al., 2008), and the historical relevance of its fishing grounds (Lloret and Riera, 2008), might help explain the amount and variety of litter objects encountered on its shelf and submarine canyon. Plastic was by far (80%) the most common material that made up urban litter items. This situation is similar to that encountered in most shelf and slope environments of the European continent, both in the Atlantic (e.g. [START_REF] Neves | Marine litter in bottom trawls off the Portuguese coast[END_REF][START_REF] Moriarty | Spatial and temporal analysis of litter in the Celtic Sea from Groundfish Survey data: Lessons for monitoring[END_REF][START_REF] Van Den Beld | Marine litter in submarine canyons of the Bay of Biscay[END_REF][START_REF] Maes | Below the surface: Twenty-five years of seafloor litter monitoring in coastal seas of North West Europe (1992-2017)[END_REF] and the Mediterranean Sea (e.g. [START_REF] García-Rivera | Spatial and temporal trends of marine litter in the Spanish Mediterranean seafloor[END_REF][START_REF] Gerigny | Seafloor litter from the continental shelf and canyons in French Mediterranean Water: Distribution, typologies and trends[END_REF][START_REF] Spedicato | b marine macro-litter on the seafloor in the northern Mediterranean Sea: the MEDITS initiative[END_REF]. Most items were small sized, and included plastic bags and bottles, but also clothes and other daily use objects. These items were possibly brought from surrounding areas by the wind or terrestrial run-off mainly during torrential events [START_REF] Rech | Rivers as a source of marine litter -A study from the SE Pacific[END_REF], or even discarded directly on beaches or at sea [START_REF] Tubau | Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes[END_REF]. However, due to the particularities of the Gulf of Lion, the likelihood of an allochthonous origin of at least part of the lighter fraction should not be ruled out, with items reaching the sea from rivers that discharge in other parts of the gulf (Castro-Jiménez et al., 2019) and transported following the dominant water circulation patter [START_REF] Millot | The Gulf of Lions' hydrodynamics[END_REF]. Conversely, the presence of some very large items such as fuel drums and car tires are an indication of intentional dumping, likely from the side or the back of vessels, a al., 2011;[START_REF] Strafella | Spatial pattern and weight of seabed marine litter in the northern and central Adriatic Sea[END_REF]. Although it is difficult to determine how long these objects have been at the seafloor, their presence might relate to practices that were more common in past decades, when the legislation on ocean dumping was less restrictive and the collection of waste by port authorities was not as widespread as it is nowadays (MARPOL, 1988).

García

y h E ' ( . .
The overall density of 110 litter items ha -1 registered in Cap de Creus is of a similar magnitude to that found in the close-by submarine canyon of La Fonera, located only 50 km south (150 items ha -1 ; [START_REF] Tubau | Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes[END_REF].

However, imaging studies carried in other shelf and upper slope areas of the Mediterranean have reported litter densities up to one order of magnitude higher than those found in Cap de Creus, for example in the Ligurian basin (1500 items ha -1 , Enrichetti et al., 2020 and[START_REF] Bo | Fishing impact on deep Mediterranean rocky habitats as revealed by ROV investigation[END_REF] and the Tyrrhenian Sea (1200 items ha -1 , [START_REF] Angiolillo | Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy)[END_REF]. Such differences must be attributed to the higher number of abandoned fishing gears that can be found on the seabed of the Central Mediterranean, where deep rocky banks and submarine canyons are highly frequented by local fishermen (e.g. [START_REF] Angiolillo | Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy)[END_REF][START_REF] Cau | Submarine canyons along the upper Sardinian slope (Central Western Mediterranean) as repositories for derelict fishing gears[END_REF][START_REF] Consoli | Marine litter from fishery activities in the Western Mediterranean sea: The impact of entanglement on marine animal forests[END_REF]Enrichetti et al., 2020). In Cap de Creus, densities of ALDFG peaked at the canyon head (150-400 m), where more than 90% of litter items encountered were fishing-related.

This situation was primarily associated to the large number of entangled longlines observed in the images, which generated an average density of 219 lines ha -1 for the canyon head. Very high abundances, in excess of 1000 lines ha -1 , were reported in some spots, being Dive 9 the most characteristic example, with 119 lines annotated in a transect of less than 500 m in length.

This situation seems to relate directly to the artisanal fishery that has been practiced in the area for a long time (Lloret and Riera, 2008), and even though the number of active longlining boats has steadily declined during the past decades [START_REF] Gómez | The decline of the artisanal fisheries in Mediterranean coastal areas: the case of Cap de Creus (Cape Creus)[END_REF], its imprint remains visible in the steepest areas of the canyon head. As in Cap de Creus, the presence of lost longlines has become very common in seamounts and submarine canyons worldwide since these gears get easily entangled on hard grounds [START_REF] Macfadyen | Abandoned, Lost or Otherwise Discarded Fishing Gear[END_REF][START_REF] Pham | Abundance of litter on Condor seamount (Azores, Portugal, Northeast Atlantic)[END_REF]. Lost lines and cables have now been reported in almost all submarine canyons across European continental margins, such as the canyon system of the Gulf of Lion [START_REF] Fabri | Megafauna of vulnerable marine ecosystems in French mediterranean submarine canyons. Spatial distribution and anthropogenic impacts[END_REF][START_REF] Gerigny | Seafloor litter from the continental shelf and canyons in French Mediterranean Water: Distribution, typologies and trends[END_REF] and bottom-trawling nets may represent in some places a significant contribution to seafloor ALDFG [START_REF] Macfadyen | Abandoned, Lost or Otherwise Discarded Fishing Gear[END_REF].

Seafloor litter transport

Urban litter items showed a very clear spatial distribution pattern, with densities rapidly increasing with water depth (Figure 3). The deepest domain explored (i.e. the middle canyon, from 1000 to1600 m depth) was the one showing the highest density of urban litter items (188 items ha -1 ), 25 times higher than on the mid and outer continental shelf (7.2 items ha -1 ; see Section 3.2). A similar situation has been described in other deep-sea areas of the Mediterranean Sea, where large accumulations of debris appears below 1300-1500 m depth, such as the submarine canyons in the Messina Strait [START_REF] Pierdomenico | Massive benthic litter funnelled to deep sea by flash-flood generated hyperpycnal flows[END_REF] or the abyssal plains of the Sardinian margin [START_REF] Cau | Dumping to the abyss: single-use marine litter invading bathyal plains of the Sardinian margin (Tyrrhenian Sea)[END_REF].

Beyond the topographic trap effect driven by gravity of submarine canyons, the litter distribution observed in Cap de Creus Canyon, with much more urban litter items in distal deeper areas than on the shore-proximal shallower shelf, must be explained by the dynamics of local bottom currents. Evidence indicates that the strong currents that recurrently sweep out the seafloor off Cap de Creus peninsula [START_REF] Canals | Flushing submarine canyons[END_REF][START_REF] Ulses | Dense shelf water cascading in the northwestern Mediterranean during the cold winter 2005: Quantification of the export through the Gulf of Lion and the Catalan margin[END_REF][START_REF] Durrieu De Madron | Interaction of dense shelf water cascading and open-sea convection in the northwestern Mediterranean during winter 2012[END_REF] must be the causative process for such an asymmetric distribution, as they have the capability to carry light urban litter items towards the deepest parts of the submarine canyon, which ultimately becomes an accumulation area. Indeed, erosive and tractive features over the continental shelf embracing the Cap de Creus Canyon and on the canyon southern wall and floor have been also related to sediment-laden, strong bottom flows generated by dense shelf water cascading [START_REF] Canals | Flushing submarine canyons[END_REF][START_REF] Lastras | A walk down the Cap de Creus canyon, Northwestern Mediterranean Sea: Recent processes inferred from morphology and sediment bedforms[END_REF][START_REF] Puig | Dense shelf water cascades and sedimentary furrow formation in the Cap de Creus Canyon, northwestern Mediterranean Sea[END_REF][START_REF] Durán | Morphology and sediment dynamics of the northern Catalan continental shelf, northwestern Mediterranean Sea[END_REF][START_REF] Ribó | Large sediment waves over the Gulf of Roses upper continental slope (NW Mediterranean)[END_REF]. In situ near bottom (i.e. 30 m above bottom) current speeds within Cap de Creus Canyon measured at the occasion of dense shelf water cascading events during the last two decades illustrate marine litter transport patterns to the deep [START_REF] Canals | Flushing submarine canyons[END_REF][START_REF] Sanchez-Vidal | Delivery of unprecedented amounts of perfluoroalkyl substances towards the deep-sea[END_REF]. Large volumes of dense water form over the continental shelf of the Gulf of Lion when strong, persistent, cold and dry northerly winds enhance heat losses and cool off shelf surface waters, thus increasing their density. The dense shelf water then flows cyclonically over most of the shelf on a southwestwards-oriented regional circulation pattern. Flow lines converge and flow accelerates because of an obstacle effect produced Cap de Creus Peninsula, in the southwestern part of the gulf.

The cape deviates the water course seawards, thus flowing down into the canyon head an upper course, also favored by the narrowing of the shelf shoreward of the canyon head (Figure 6). This process has been identified in many locations both in the Mediterranean Sea and the world ocean [START_REF] Ivanov | Cascades of dense water around the world ocean[END_REF][START_REF] Durrieu De Madron | w h w[END_REF][START_REF] Canals | Cascades in Mediterranean Submarine Grand Canyons[END_REF]. Amongst the many canyons in the Gulf of Lions and on the North Catalan continental margin, Cap de Creus Canyon is the main outlet for dense shelf water cascading (and everything else that comes with), which is undoubtedly favored by its location with respect to the regional circulation ahead of the promontory formed by the Cap de Creus Peninsula [START_REF] Canals | Flushing submarine canyons[END_REF]. The erosional, tractive and depositional effects of these cascades on the canyon floor are clearly visible down to its mouth at 2140 m depth and beyond are illustrated by giant furrows, an incised thalweg, scours, sediment bars and coarse sand deposits [START_REF] Lastras | A walk down the Cap de Creus canyon, Northwestern Mediterranean Sea: Recent processes inferred from morphology and sediment bedforms[END_REF].

During such events, dense cascading shelf waters carry huge amounts of resuspended sediments downcanyon, together with organic matter and pollutants advected from the continental shelf [START_REF] Guillén | Sediment dynamics during wet and dry storm events on the Têt inner shelf (SW Gulf of Lions)[END_REF][START_REF] Bourrin | Sediment dispersal from a typical Mediterranean flood: The Têt River, Gulf of Lions[END_REF][START_REF] Sanchez-Vidal | Impact of dense shelf water cascading on the transfer of organic matter to the deep western Mediterranean basin[END_REF], 2015;[START_REF] Salvadó | The role of dense shelf water cascading in the transfer of organochlorine compounds to open marine waters[END_REF][START_REF] Salvadó | Transfer of lipid molecules and polycyclic aromatic hydrocarbons to open marine waters by dense water cascading events[END_REF]. The finest fraction of such sedimentary flows can stay in suspension for long periods of time (i.e. some years) thereby forming hundreds of meters thick nepheloid layers extending over the slope and deep basin [START_REF] Puig | Thick bottom nepheloid layers in the western Mediterranean generated by deep dense shelf water cascading[END_REF].

This proves that light micro-and macrolitter (e.g. plastics) lying on the continental shelf may easily be swept and transported all the way down the Cap de Creus submarine canyon. Because of their intrinsic properties, plastic items (bags, bottles, cups, fragments) with low drag area behave noncohesively in marine conditions. Turbulent bottom cascading currents are able to provide the shear stress needed to resuspend and transport these objects, either as bed load (relatively heavier items), or by saltation or suspension (relatively lighter items). Conversely, longlines and ropes, and nets would not have been dragged downcanyon since they usually are strongly caught around outcropping rocks, hard grounds and cold-water coral colonies (see Sections 3.2 and 3.4) in the canyon head, thus severely limiting chances for transportation. Other ALDFG items, such as bottom trawling nets found on soft bottoms, would seem too big and heavy to be transported by those currents. However, it has been observed for these currents to cause about 400 kg mooring anchor weights left on the sand-filled canyon thalweg to move down by several kilometers while dragging the entire mooring just in few days [START_REF] Puig | Dense shelf water cascades and sedimentary furrow formation in the Cap de Creus Canyon, northwestern Mediterranean Sea[END_REF], which illustrates the tremendous transport capacity these currents have. In fact, the highest number of bottom trawl nets reported in this study (Dive 42) appeared in an area of the canyon head that according to VMS records (unpublished data) is not frequented by trawlers. This could be an indication that bottom trawl nets abandoned on the northern shelf could be pushed towards the canyon head, where they could end up entangled around rocks. All the above provides a robust explanation of the litter class sorting observed in Cap de Creus Canyon, with ALDFG concentrating in the canyon head and lighter objects being washed away to the deepest part of the canyon floor. [START_REF] Tubau | Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes[END_REF] had formerly suggested the above-described litter funneling process towards deeper canyon reaches, which then become litter accumulation zones. The results presented here bring in a wealth of data from [START_REF] Dominguez-Carrió | ROV-based ecological study and management proposals for the offshore Marine Protected Area of Cap de Creus[END_REF][START_REF] Cau | Microplastics in the crustaceans Nephrops norvegicus and Aristeus antennatus: Flagship species for deep-sea environments?[END_REF], which could introduce this fragmented plastic into the food chain and eventually generate problems of food security.

Interactions of longlines with cold-water corals

It has been recognized that longline fishing has a far smaller impact on vulnerable marine ecosystems than commercial bottom trawling (Pham et al., 2014a). This does not mean that its effects over the benthic fauna should be overlooked, especially in coral rich areas where an intense activity of bottom longlining exists [START_REF] Bo | Fishing impact on deep Mediterranean rocky habitats as revealed by ROV investigation[END_REF][START_REF] Consoli | Marine litter from fishery activities in the Western Mediterranean sea: The impact of entanglement on marine animal forests[END_REF]. We have assessed the impact of abandoned longlines on the three main cold-water coral species occurring in Cap de Creus Canyon as a proxy for the level of impact this fishing practices may have over the benthic community in its entirety.

Whereas the number of coral colonies affected differed from one dive to another, the highest percentage of entanglement occurred in areas where the density of longlines was higher. Overall, 10% of all cold-water colonies identified in the video footage had lines entangled around them, a situation that could lead to suffocation, branch breakage, abrasion, epibiosis, infection and ultimately the death of colonies [START_REF] Galgani | Marine animal forests as useful indicators of entanglement by marine litter[END_REF]. Compared to other locations in the Mediterranean Sea, where up to three times more corals have been reported to be affected by longlines [START_REF] Angiolillo | Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy)[END_REF][START_REF] Bo | Fishing impact on deep Mediterranean rocky habitats as revealed by ROV investigation[END_REF], the value we have found in Cap de Creus Canyon appears rather low.

However, video footage may offer a partial view of the real impact caused by longlines, as it provides limited information on how many colonies are partially broken and no information at all on colonies that have been fully removed from their natural habitat due to such fishing practices. If properly recorded, by-catch data from fishing boat logbooks could bring complementary information to better assess the percentage of coral colonies broken or entirely removed by longlining yearly. It seems also plausible that loose longlines, ropes and net fragments, together with their loose ends and hanging sections, could be swung and moved down by the strong bottom currents measured in the Cap de Creus canyon head and beyond. This might favor secondary entanglement around already entangled colonies and on new colonies, with the associated damage this could cause.

Management implications

As part of the ecosystem-based approach to management that should be In the same way, abandoned trammel and trawl nets could also be retrieved to reduce future damage. Although these procedures are much simpler in shallow waters, where SCUBA divers can operate generating the minimum damage possible (see a protocol for the extraction of lost nets in Hereu and Ylla, 2017), there exists the possibility of using, for instance, a vessel-towed " " (G h . 2009) to retrieve selected nets from deeper softbottom areas. Such an operation, which has proven satisfactory to remove gillnets in deep-sea areas in Norway and Rockall and Porcupine banks [START_REF] Large | Lost and abandoned nets in deep-water gillnet fisheries in the Northeast Atlantic: retrieval exercises and outcomes[END_REF], would be relatively cheap and simple to implement. Joint actions with local fishermen, who have a strong knowledge of the seabed after many years of experience, could facilitate the retrieval of ALDFG, while helping raising awareness of the impacts that their activities may have over the benthic ecosystem and, ultimately, in the catches they are interested in.

Initiatives such as Fishing for Litter (www.fishingforlitter.org.uk), Projecte Marviva (http://residus.gencat.cat/ca/ambits_dactuacio/tipus_de_residu/deixallesmarines/projectes/projecte-marviva/) and Projecte Evitem la Pesca Fantasma (http://www.pescafantasma.cat/) could serve as useful references for the retrieval of abandoned fishing arts.

Finally, and following the demands of the MSFD, the data provided in this study should be view as a robust reference point in order to monitor the temporal evolution of the marine area, and also to determine the effectiveness of management and mitigation actions developed by regional and national authorities in the forthcoming years.

Funding

The Each circle corresponds to one dive. Isobaths in meters. Tables 1-2

Table 2. Number of cold-water coral colonies and per species percentage of entanglement with longlines as observed in the 8 canyon head dives evaluated for this study where cold-water corals were present. All dives were performed at depths between 215 and 390 m. Longline density expressed both as items per ha and items per 100 linear meters.

  dives performed during 5 oceanographic cruises between 2007 and 2013, as part of the HERMES, DEEP CORAL, PROMARES and Life+ INDEMARES projects. Four different underwater vehicles were used: the manned submersible JAGO (GEOMAR, Germany), the commercial ROV Liropus 2000(IEO, Spain), the purpose built ROV Nemo (Gavin Newman, UK) and the small and compact ROV Bleeper EVO (ICM-CSIC, Spain). All vehicles but Bleeper EVO were equipped with an HD camera and a USBL system to obtain accurate positions of the vehicle over the seabed, with a time frequency below 20 seconds. Bleeper EVO, which was only used on the continental shelf, had an SD definition camera and its position was inferred from that of the vessel and the angle of the cable when being towed over the seafloor. Geographic positioning data was used to calculate the distance travelled by the underwater vehicle in each dive. All platforms were equipped with parallel lasers to provide scale to the images. Metadata regarding each

  was used to calculate the bottom currents in the study area. This model classically solves the equations for temperature, salinity and the two components of horizontal current starting from initial conditions and using time-dependent forcing. The horizontal grid was designed to study the connections between the Gulf of Lions and the Catalan region with the south of the basin through the formation and dispersion of dense water. The resulting curvilinear grid had a pole positioned in the Pyrenees, allowing a minimum resolution of about 700 m near the French and Catalan coast, and increasing to reach 5-6 km near Algeria.The model was initialized and forced at its open boundaries by the NEMOMED8 model described in[START_REF] Herrmann | What induced the exceptional 2005 convection event in the northwestern Mediterranean basin? Answers from a modeling study[END_REF]. At the surface, the same atmospheric forcing than this model was used i.e. the ARPERA dataset[START_REF] Herrmann | Relevance of ERA40 dynamical downscaling for modeling deep convection in the Mediterranean Sea[END_REF], which is a dynamic downscaling of the ERA40 climate model reanalysis and of the ECMWF (European Centre for Medium-Range Weather Forecasts) model reanalysis since 2001. This forcing consists in daily averaged wind stress, solar flux, long wave net heat flux, sensible and latent heat flux and precipitation, leaving the diurnal cycle unresolved. The sea surface temperature was nudged towards the climatological one used in the NEMOMED8 model, ensuring the consistencybetween the two models. The two components of the horizontal current were then extracted from the daily outputs of the model, rotated to be along the WE and NS axis and interpolated on a regular grid. The simulations were run from the beginning of year 2000 to the end of 2013, and the daily currents for the month of February 2012 were averaged to illustrate the strength of bottom currents in the area. This month was chosen because it is known to be an exceptional period of dense water formation on the Gulf of Lion shelf, with deep cascading in Cap de Creus Canyon (Durrieu deMadron et al., 2013;[START_REF] Sanchez-Vidal | Delivery of unprecedented amounts of perfluoroalkyl substances towards the deep-sea[END_REF], a recurrent process known to occur periodically in the area. Although extreme deep-cascade events are not very frequent (highintensity events recorded in 1999, 2005 and 2012; e.g.[START_REF] Canals | Flushing submarine canyons[END_REF][START_REF] Ulses | Dense shelf water cascading in the northwestern Mediterranean during the cold winter 2005: Quantification of the export through the Gulf of Lion and the Catalan margin[END_REF][START_REF] Durrieu De Madron | Interaction of dense shelf water cascading and open-sea convection in the northwestern Mediterranean during winter 2012[END_REF],[START_REF] Mikolajczak | Impact of storms on residence times and export of coastal waters during a mild autumn/winter period in the Gulf of Lion[END_REF] estimated that during the period 2010-2017, one year out of two, cascading could affect depths of 1000 m, while in the remaining years it would only sporadically reach 500 m depth.

  plastic and glass bottles, shopping bags, tin cans and clothes of different sorts (examples in Figure2a-c). Very few items reached large sizes (>1m) besides some car tires and an oil drum (Figure2d,e). The abundance of urban litter was generally low across dives, although density values exceeded 100 items ha -1 in 4 transects(8-26-39-40). Plastic was the main component, with almost 80% of all urban litter objects completely made of plastic or included plastic parts. Six amphorae were also identified in the footage (Figure2f). About 53% of the total number of litter items (439) were classified as abandoned, lost or otherwise discarded fishing gears (ALDFG). The vast majority corresponded to longlines, with 371items (85% of ALDFG; examples in Figure2g,h). The number of bottom trawl nets and cables was much lower (56 items, 13%; examples in Figure2i,j), and trammel nets were the least common type of fishing gear, with only 12 items observed (3% of all ALDFG; examples in Figure2k,l).

  m cells) is shown in Figure6. As shown by the model, after a very intense cascading event, coastal waters can reach the base of the slope, at depths in excess of 1500 m. Bottom currents associated with this process are gravity currents whose intensity is proportional to the bathymetric slope. The acceleration of the current at the end of the shelf, first between 100 and 200 m depth, and then beyond 200 m inside the canyon, can generate flow velocities above 1 m s -1 . Highest current speeds are found on the southern part of the canyon head and the upper canyon, where the dense water vein penetrates with a significant angle of incidence with respect to the isobaths.Further downstream, under the action of the Coriolis force that deflects the current to the right, the dense water vein is progressively flattened along the southern flank of the canyon, which produces a decrease of the current strength. Currents of up to 30 cm s -1 are also present on the external part of shelf, corresponding to water masses less dense than those that penetrate in the canyon. Regarding the realism of the simulation, currents above 1 m s -1 were measured in February 2012 at depths of 1000 m in the canyon axis, with a current meter located 23 m above the seafloor[START_REF] Sanchez-Vidal | Delivery of unprecedented amounts of perfluoroalkyl substances towards the deep-sea[END_REF].

  providing and improved understanding of the magnitude of the cleaning role of the continental shelf by high-energy natural oceanographic processes. Finally, it could be hypothesized that these processes may have an even larger influence on the distribution of microplastics at larger scale, since small plastic particles could be easily washed away through submarine canyons towards deeper areas, generating accumulations areas beyond 2000 m, as already suggested by[START_REF] Sanchez-Vidal | The imprint of microfibres in southern European deep seas[END_REF]. The presence of large deposits of microplastics on the deep sea could have far reaching consequences than previously thought, especially if they become part of the diet of some deep-sea species (Carreras-Colom et

  consider using the results of this study when designing mitigation measures to tackle the threat posed by the accumulation of marine litter over the seabed. In this sense, maintaining or improving the quality of the marine ecosystem of Cap de Creus could only be achieved by means of (1) a drastic reduction of the litter inputs (i.e. strict control of land and sea-based sources) and possibly (2) through specific actions set to remove some of the objects currently found over the seabed. The development of such measures would be in line with initiatives already launched at the European level (e.g. European Commission, 2019), which are now seeking solutions for the removal of existing marine litter (notably plastics and microplastics) to limit the damage over the benthic ecosystem. In the specific case of Cap de Creus, since all litter items identified in the video footage are now accurately georeferenced, it could be possible to attempt the recovery of some of the debris found in certain accumulation areas or litter hotspots, especially in trawlable grounds inside the submarine canyon. In these cases, each attempt should weight the benefits of removing large amounts of marine litter against the potential impact on the benthic fauna produced by trawl net, especially in those areas that are currently free of trawling. The video images used together with the multibeam bathymetry of the submarine canyon could be a powerful tool to assess the feasibility of each action and the consequences of its implementation.

Figure 2 .

 2 Figure 2. Examples of litter items found in the underwater video transects

Figure 3 .

 3 Figure 3. Seafloor litter density for each category of urban litter (colored) and

Figure 4 .

 4 Figure 4. Distribution and density of marine litter in Cap de Creus mid and

Figure 5 .

 5 Figure 5. Examples of litter accumulation areas " h " h

Figure 6 .

 6 Figure 6. Model of the average bottom current speed offshore Cap de Creus

Figure 7 .

 7 Figure 7. Some examples of how the bottom longlines get entangled around

  Location of the mid-point of the 68 underwater video transects carried out in Cap de Creus mid and outer shelf and submarine canyon to assess the occurrence, abundance and composition of seafloor litter. Dashed lines correspond to the isobaths defining the limits of the inspected domains:

	(LIFE07/NAT/E/000732) funded the 2009, 2010 & 2012 cruises on board R/V Garcia del Cid and the littoral surveys with Bleeper EVO in 2009 and 2013. Numerical simulations were performed using HPC resources from the CALMIP platform (French region Occitanie) under grant P09115. The SYMPHONIE model is distributed by the SIROCCO group Figure 1. northern shelf and southern shelf (80-150 m), canyon head (250-400 m),
	(https://sirocco.obs-mip.fr). This work also is a contribution of project IDEM upper canyon (400-1000 m) and middle canyon (1000-1600 m). The actual
	(Implementation of the MSFD to the DEep Mediterranean Sea, ref. path of the dives is not show on the map, but start-end positions of each dive
	11.0661/2017/750680/SUB/ENV.C2) funded by DG Environment of the can be found in Supplementary Table 1. Isobaths in meters.
	European Commission, and the research network Red Española sobre
	BAsuras MARinas (BAMAR, CGL2016-81854-REDT) coordinated by the
	University of Barcelona.
		European Project HERMES (Goce-CT-2005-511234-I), the Spanish
	Project DEEP CORAL (CTM2005-07756-C02-02/MAR) and the Acciones
	Complementarias (CTM2007-28758-E/MAR) supported the 2007 cruise on
	board R/V Garcia del Cid with the manned submersible JAGO.	ó "
		x "	h	RO ARE ROV		h	y
	for which IEO and CSIC provided the Liropus 2000 ROV and R/V Sarmiento
	de	Gamboa,	respectively.	The	EU	project	Life+	Indemares

Table 1 .

 1 Metadata and number of litter items for each of the 68 underwater video transects examined in this study. Geographical positions correspond to approximately the middle point of each dive. Domains: NS: northern shelf (80-150m); SS: southern shelf (80-150m); CH: canyon head (150-400m); UC: upper canyon (400-1000m); MC: middle canyon (1000-1600m). ALDFG: abandoned, lost or otherwise discarded fishing gear.

	Dive	Date (dd/mm/yy)	Position Lat. N Long. E	Vehicle	Depth range (m)	Domain	Analyzed area (m 2 )	Urban items (n)	ALDFG (n)
	1	09/09/07	42.3896	3.3142	JAGO	215-186	CH	144		18
	2	09/09/07	42.3497	3.3585	JAGO	386-377	CH	406		11
	3	10/09/07	42.3882	3.3159	JAGO	199-173	CH	1108		45
	4	12/09/07	42.3869	3.3209	JAGO	302-302	CH	196		8
	5	13/09/07	42.3784	3.3283	JAGO	316-302	CH	516	3	18
	6	13/09/07	42.3955	3.3033	JAGO	168-153	CH	324
	7	14/09/07	42.3575	3.3358	JAGO	234-236	CH	944	4	31
	8	15/09/07	42.3704	3.3376	JAGO	293-264	CH	376	6	34
	9	15/09/07	42.3919	3.3129	JAGO	282-165	CH	970	1	119
		25/08/09	42.3702	3.2988	Bleeper EVO	109-110	NS	452	1	1
		26/08/09	42.3471	3.3093	Bleeper EVO	115-112	NS	41.5
		26/08/09	42.3397	3.3167	Bleeper EVO	98-95	NS	279.5
		26/08/09	42.3691	3.2606	Bleeper EVO	99-99	NS	507.5		1
		27/08/09	42.3924	3.2569	Bleeper EVO	97-99	NS	338
		27/08/09	42.3839	3.2719	Bleeper EVO	102-103	NS	238
		27/08/09	42.3929	3.2882	Bleeper EVO	107-107	NS	86.5
		27/08/09	42.3900	3.2924	Bleeper EVO	106-107	NS	219
		27/08/09	42.3404	3.3354	Bleeper EVO	111-117	NS	218		1
		23/09/09	42.3795	3.2690	Nemo ROV	102-101	NS	662	1
		23/09/09	42.3862	3.3044	Nemo ROV	111-111	NS	252
		23/09/09	42.3569	3.3269	Nemo ROV	151-118	NS	218
		24/09/09	42.3632	3.2977	Nemo ROV	111-108	NS	146		2
		26/09/09	42.3945	3.3035	Nemo ROV	148-142	NS	41.5
		27/09/09	42.3636	3.3303	Nemo ROV	166-160	CH	203		5
		27/09/09	42.3667	3.3185	Nemo ROV	121-115	NS	312.5
		27/09/09	42.3443	3.3081	Nemo ROV	111-94	NS	284.5	3	3
		28/09/09	42.3317	3.3623	Nemo ROV	130-148	SS	118.5
		28/09/09	42.3833	3.2646	Nemo ROV	100-99	NS	234.5
		28/09/09	42.3852	3.2696	Nemo ROV	102-101	NS	203
		29/09/09	42.3310	3.3706	Nemo ROV	160-150	CH	43
		29/09/09	42.3851	3.4001	Nemo ROV	137-137	NS	45
		13/06/10	42.3085	3.3965	JAGO	116-117	SS	1868		18
		13/06/10	42.3096	3.4368	JAGO	132-128	SS	1188		5
		14/06/10	42.2635	3.3403	JAGO	94-94	SS	1320
		17/06/10	42.2852	3.4608	JAGO	127-125	SS	1872		4
		18/06/10	42.3078	3.3624	JAGO	108-114	SS	1728	4	23
		03/07/11	42.3315	3.4656	Liropus 2000	156-790	CH / UC	15525	34	10
		04/07/11	42.3470	3.4631	Liropus 2000	681-795	UC	9923.4	60
		05/07/11	42.2227	3.8298	Liropus 2000	1491-1570	MC	6456.3	69
		05/07/11	42.2847	3.6399	Liropus 2000	1198-1245	MC	5789.1	161	5
		06/07/11	42.3562	3.3361	Liropus 2000	248-299	CH	863.1	2
		06/07/11	42.3782	3.3332	Liropus 2000	270-371	CH	1375.8	3	19
		06/07/11	42.3888	3.3709	Liropus 2000	176-321	CH	1998.3	9	7
		07/07/11	42.3771	3.3541	Liropus 2000	387-522	UC	8814	28	5
		06/07/12	42.2712	3.4109	Nemo ROV	126-126	SS	252.5
		06/07/12	42.2946	3.4236	Nemo ROV	127-126	SS	174		1
		06/07/12	42.3070	3.4454	Nemo ROV	147-129	SS	373.5		8
		07/07/12	42.3393	3.3505	Nemo ROV	128-125	NS	415	1	1
		07/07/12	42.3366	3.3272	Nemo ROV	99-96	NS	173	1	5
		07/07/12	42.3452	3.3226	Nemo ROV	108-109	NS	202.5		1
		07/07/12	42.3435	3.2948	Nemo ROV	90-88	NS	89		2
		07/07/12	42.3412	3.3360	Nemo ROV	115-116	NS	89
		08/07/12	42.3344	3.3249	Nemo ROV	98-91	NS	381.5		8
		08/07/12	42.3572	3.2770	Nemo ROV	103-97	NS	432.5		1
		08/07/12	42.3698	3.2832	Nemo ROV	109-105	NS	287
		09/07/12	42.3967	3.2840	Nemo ROV	108-104	NS	279
		09/07/12	42.3219	3.3678	Nemo ROV	127-123	SS	436		1
		09/07/12	42.3463	3.3184	Nemo ROV	107-102	NS	474.5	2	9
		09/07/12	42.3514	3.2897	Nemo ROV	96-98	NS	142		1
		09/07/12	42.3808	3.3177	Nemo ROV	210-115	CH / NS	544.5
		09/07/12	42.4115	3.2536	Nemo ROV	98-98	NS	139.5
		09/07/12	42.3056	3.4305	Nemo ROV	124-129	SS	395.5		5
		10/07/12	42.3004	3.3671	Nemo ROV	116-118	SS	92		3
		10/07/12	42.3021	3.3567	Nemo ROV	101-96	SS	287.5
		27/01/13	42.2989	3.3492	Bleeper EVO	90-96	SS	319.5
		06/06/13	42.2824	3.3394	Bleeper EVO	90-92	SS	300.5
		14/10/13	42.2726	3.3080	Bleeper EVO	83-79	SS	163.5
		04/12/13	42.2677	3.3780	Bleeper EVO	121-121	SS	445.5	1

Acknowledgements

The authors would like to thank the crew of the research vessels and all the scientists and technicians that helped during the different surveys. We are grateful for the professionality shown by Gavin Newman (ROV pilot) and the members of the JAGO Team Jurgen Schauer and Karen Hissman during the acquisition of the video footage during the DEEP CORAL and INDEMARES cruises. Generalitat de Catalunya autonomous government funding to CRG Marine Geosciences is also acknowledged (Ref. 2017 SGR 315).


Benny Sluchin
email: benny.sluchin@ircam.fr

Mikhail Malt
email: mikhail.malt@ircam.fr

A COMPUTER AIDED INTERPRETATION INTERFACE FOR JOHN CAGE'S NUMBER PIECE TWO 5

Conceptual musical works that lead to a multitude of realizations are of special interest. One can't talk about a performance without taking into account the rules that lead to the existence of that version. After dealing with similar works of open form by Iannis Xenakis, Pierre Boulez and Karlheinz Stockhausen, the interest in John Cage's music is evident. His works are "so free" that one can play any part of the material; even a void set is welcomed. The freedom is maximal and still there are decisions to consider in order to make the piece played.

Cagener, is a project intended to develop a set of conceptual and software tools, that generates a representation of the work. It may be played live or showed as a sonorous installation. We deal here with the Number Pieces he composed in the last years of his life. The project calls for sound techniques, logic and musicological knowledge of the 21 st century to approach the original ideas of the composer. The computer serves as a partner in making choices of multiple possibilities, mix together sounds of different sources and of various kinds and following compositional ideas clearly stated. The role of the sound projection in space is an important part of the studio preview.

INTRODUCTION

The performer approaching John Cage's music composed after the middle of the 20 th century is often surprised to encounter a large amount of freedom mixed with a set of precise instructions. As a common result, the musician will determine "a version" in which he will decide on the free elements included in the score. A fixed score is thus created and used repeatedly. The performer will play it without any doubts of the composer's intentions. In fact, most of Cage's scores after the fifties are not to be pre-generated. Each performance should be unique and undetermined. Using the computer helps one to perform, ignoring what and when he is going to play.

SILENCE AND INDETERMINANCY IN JOHN CAGE'S EARLY PIECES

In connection with his encounter with Zen Buddhism [1], Cage rethinks his understanding of music. As a result, he composes 4'33", a work whose abandonment of intentional sound production drew controversy to his compositions. Cage spoke of silence in a new and positive way. Not only has it an importance in the creation of structure but one has to think of it not as an absence of sound but as a presence to fill an acoustical space.

The three kinds of "silence"

At first, Cage developed a structural concept of silence, considering it as an absence of sound helping to structure the music by its alternation with sound. The silence between the notes gave the work its cohesion. Later Cage adopted a spatial concept of silence, in which it was composed of all the ambient sounds that together formed a musical structure. Finally his concept evolved towards viewing silence as non-intention. Both sound and silence would exist only in the non-intention manner of nature [START_REF] James | Non-intentional performance practice in John Cage's solo for sliding trombone[END_REF].

What is indeterminacy?

The principal of indeterminacy allows the performers to work independently from each other. In this way, the musician ignoring the output of his fellow musicians will concentrate on his own part and the set of instructions, which imposes concentration even if degree of the freedom involved is high [START_REF] Pritchett | The Music of John Cage[END_REF].

The Number Pieces

In Cage's Number Pieces, each individual part contains musical events endowed with time brackets, giving the player lower and upper bounds of time for starting and ending each event (Figure 1, Figure 2). The piece has a definite duration, and the elements occur within the given time brackets. In spite of the fact that only individual parts exist, an ensemble score is implicitly present and yields a strong form [START_REF] Haskins | The Number Pieces of John Cage[END_REF].

THE DIFFICULTY ON PERFORMING JOHN CAGE'S INDETERMINATE WORKS

It is the freedom relationship pre-determination that gives the player the main problem. Even if we find very hard instrumental passages, the main difficulties are: making the choice of when and what is to be played, what order to choose for the elements, the amount of silence to insert between the events, and all this while ignoring the output of the other musicians involved. It has to be kept in mind that by the absence of intention, one should also ignore what he himself is about to perform. This means, that the entire score should be at the player's disposal, and that he will make up his mind intuitively and spontaneously. This research was initiated by that concern. We have approached first Two 5 and Five 3 , as our initial concern pieces with trombone. The interface developed and the analytical results are easily applicable to any of the Number Pieces.

PERFORMING CONTEXT

Cage instructions

Cage's instructions in the TWO 5

Perfomance particularities

The "Number Pieces", in general, seem to be easy to perform, not presenting special instrumental difficulties. Concerning the way Cage's chooses the "material to fit in the time brackets" Benedict Weisser [START_REF] Benedict Weisser | Notational Practice in Contemporary Music: a Critique of Three Compositional Models[END_REF] point out the fact that:

"For as time passed, Cage was filling the boxes with progressively less and less." [START_REF] Benedict Weisser | Notational Practice in Contemporary Music: a Critique of Three Compositional Models[END_REF][94][95]] What Weisser call "boxes" is what we define as a "generic musical event". As Two 5 was composed in 1991, close to Cage's death, this statement gives some explanation concerning the scarcity of the material used. As there are very few elements every detail becomes important, as for example the attacks and releases of single notes, the simultaneity of chords, pedal actions that could bring unwanted noise or any other external sound source. The main difficulty consists in being "a tool" to make the composer's work comes to live. The musicians have to enter in a special state of mind where the awareness of quality of sound and the quality of silence are important. For this reason a "meditative concentration" is needed.

TOOLS FOR COMPUTER ASSSITED PERFORMANCE, CAP

What is "computer assisted performance"

The musical world offered itself a multitude of tools with the evolution of computer technologies. At first, dedicated to an employment in musical composition, they were oriented and adapted to a use in musical analysis and as aid tools to interpretation [START_REF] Malt | L'interprétation assistée par ordinateur[END_REF].

Several practices concerned with the interpretation field were developed. One can mention:

• The use of audio and MIDI sequencers as "super metronomes". It is common today that interpreters enter complete scores in sequencers as a way to work out difficulties in the performance (especially concerned with contemporary pieces). The musician can work progressively the problematic passages by varying the speed.

• The use of sequencers or notation programs to practice playing in ensemble. This is a logical extension of the "Minus-one" idea.

• The use of dedicated tools capable of correcting the player's interpretation.

An increasing number of composers prepare interpreters' oriented computer programs in order to help them play with the computer before starting with the actual musical piece.

There are other examples of computer tools created by or for interpreters, but our concern here is to show a new field developed in the last twenty years.

In our topic here, the interpretation of a category of Cage's work, in which the concepts of liberty and indetermination are predominant, it seems that the paper aspect of the scores is an obstacle in the realization. The wish that the interpreter could navigate freely, nondetermined and without restraint through the musical material seems opposed to the fact that the music is presented on paper, and thus in a determined order. Computers may bring a solution to that particular difficulty for Cage's and also other composers' music. The actual playing prevents the musician from doing other tasks to orient his choices in "real-time". For example Iannis Xenakis in Linaia Agon (trio for horn, trombone and tuba, 1972) asks for a passage where the different instrumental choices are directed by a "gain matrix". The choice is computer-aided in order to enable a smooth interpretation [START_REF] Sluchin | Linaia Agon, towards an interpretation based on the theory[END_REF]. Duel and Strategy, two other works by Xenakis based on Game Theory, received an analogue treatment for a CAP Interface [START_REF] Sluchin | Play and game in Duel and Strategy[END_REF]. Of different esthetics, Domaines de Pierre Boulez was investigated and lighted by an equivalent Interface [START_REF] Sluchin | Open form and two combinatorial musical models: The cases of Domaines and Duel[END_REF].

From concepts to reality

How could one help the player, as well as possible, to perform the score in a context of "indetermination" and maximum of concentration? In what manner could one enable him to represent the Cage's musical thought?

Even if hard instrumental passages are apparently missing, the main obstacles to create a required musical atmosphere are: watching the chronometer, making the choice of when start and stop to play the musical events, the amount of silence to insert between the elements of the events, the quality of silence between events and all this while ignoring the output of the other musicians involved One possible solution was to provide an adapted interface. Here the choice is not only of timing but concerns the material itself.

Modeling musical pieces

One aspect of the tools proposed here is that they are oriented towards interpretation. In that concern, the interface should "contain" implicitly or explicitly all the instructions, constraints and concepts defined by the composer, as they will establish an "experimentation field". For the construction of CAP tools, the careful study of the pieces of John Cage and its formalization is necessary. The final interface will be, in a certain way, a computer model of the particular piece.

Modeling as a step in the musical analysis process

The construction of computer models of musical pieces is not a neutral process. It is fundamental to know well the works under study, understand the constraints left by the composer, as well as the historical context of its creation. But these are still insufficient in the modeling process. Every music work has a part of liberty and ambiguity. These "holes" has to be filled up to enable the modeling process. One has to take decisions as a function of his work assumptions, founded on musical and musicological bases. The necessity to represent the score or the processes suggested by the composer on numerical, symbolic or graphic spaces has great importance. Changing the representation of an object permits to see, to consider, to observe and finally to understand it, in a different manner. The modeling process is transformed in a pragmatic analysis of the musical phenomena [START_REF] Keller | Analysis by modeling: Xenakis's ST/10 080262[END_REF].

THE "TIME-BRACKET" MODEL

There already exists an interface built for such performances [START_REF] Hajdu | Quintet.net: An Environment for Composing and Performing Music on the Internet[END_REF] and a mathematical modeling of "time-brackets" [START_REF] Popoff | Indeterminate Music and Probability Spaces: the Case of John Cage's Number Pieces[END_REF] [START_REF] Popoff | John Cage's Number Pieces: The Meta-Structure of Time-Brackets and the Notion of Time[END_REF]. Our goal was to go beyond the interface as a score substitute, proposing to performers a tool to help them to find, at best, the "meditative concentration" needed (as explained in 4.2). But also, to try to build a model, from the scarce instructions left by John Cage, trying to fill the gaps with algorithms that could represent choice and indeterminacy, leading us to a better understanding of his composer craft. We have started to work with Two 5 (1991), a piece for trombone and piano, whose duration is 40 minutes. Music strips make up the individual parts (40 for the trombone and 29 for the piano). Each one is presented in the same way (Figure 1, Figure 2): a bold number indicating the strip order, and the "timebrackets" marked above (see 2.3). An important part of our reflection was to try to figure out an interface that could present these scores to the performers. This interface should help the player in the performance, and at the same time could help in generating studio previews.

We had implemented two models, an offline in "OpenMusic"1 computer aided composition software, and a real-time one in MAX/MSP.

The first step in the process, was modeling a graphic representation of each "strip" as a musical event in time. For this, the time structure of the piece was represented as a set of events composed by the score time-line and a time vector. The time vector has the following structure:

strt 1 , strt 2 , end 1 , end 2 {
} , where strt 1 and strt 2 are the numbers in the left "time-bracket", and end 1 and end 2 the numbers in the right "time-bracket". I.e., strt 1 is the lower bound of the Starting Time Zone and strt 2 the higher one; end 1 is the lower bound of the Ending Time Zone and end 2 the higher one. The final graphic event had a trapezoidal shape (Figure 3), where the upper line represents the Starting Time Zone and the bottom line the Ending Time Zone. The height has no special meaning. More than being a graphic representation for each "strip", it allows us to identify similarities between generic musical events. For example, one can see easily the identity between the trombone generic musical events 4, 5, 14 and 26. The same comparaison done only on time brackets will be harder. We make a difference between a "generic musical event", and a "real musical event" A real musical event " i " is the one where the starting ( strt i ) and ending ( end i ) points are defined, i.e. a real musical event is a choice materilization. Where strt 1 ≤ strt i ≤ strt 2 and end 1 ≤ end i ≤ end 2 . This one could be represented by a rectangle (Figure 4). There are some properties one can easily be infered from the trapezoidal graphic representation, the generic event: 2. The maximum duration, end 2strt 1 , is the maximum length an event can have.

Ending Time Zone Starting Time Zone

3. The fact that , strt 2 > end 1 means that one can choose a starting point placed after the ending one, resulting in a void musical event. (idea so imporatnt to Cage, as he often indicates that the performer can choose, all, part, or nothing of the material to his disposal). In this case strt i > end i .

4. An implicit parameter that can be deduced is the "trapezoid slope", represented by the difference end 1strt 1 (as the heigth has no actual meaning). The slope is strongly connected with the performance. Concerning the trombone part, as it is wholy consisted of sustained notes, the knowledge of this parameter allows the performer to better manage his air capacity, in order to keep with the composer's indication. Regarding the pianist, the slope will be an information that allows him to manage his performance with regard to the time indications.

Offline model

The main purpose of the offline implementation was to study the possibility of generating several audio versions of the piece, and extracting parameters for musical analysis. For this we have built a first model in OpenMusic (Figure 5), with which we were able to:

1. Read text files with a representation of the time vectors (Figure 6), 2. Compute musical events with fixed "start and end" times, 3. Read audio recordings of each musical strip2 , 4. Rescale audio files to the durations computed in step 2, 5. Represent a Two 5 version (Figure 7) as graphical schema in a OpenMusic graphical interface (a Maquette), and 6. Save the data, derived from the calculation, in a file having the following data structure (Figure 8):

[instrument starting_time duration sound_file] As a first algorithm we used a very single random process where for each event we calculated a fixed "start_time" and a fixed "end_time" as follow:

start _ time = σ (strt 1 , strt 2 ) = strt i end _ time = σ (end 1 , end 2 ) = end i (1)
Where, Naturally, other algorithms are under study. One should mention here the probabilistically approach of Alexandre Popoff [START_REF] Popoff | Indeterminate Music and Probability Spaces: the Case of John Cage's Number Pieces[END_REF] [12].

Real time model

The real time model had as main purpose, to offer an interface for the performance; it was built in the MAX/MSP 3 graphic programming environment.

The main interface (Figure 9), has 6 fields, some may be switched on or off according to the performer's wish.

The global view -1

The global view displays a presentation of the entire duration of Two 5 , using the trapezoidal event representation. It allows the performer to have a global view of the piece at a glance. As Cage mention about the context-specific character of his time-bracket notation:

"Then, we can foresee the nature of what will happen in the performance, but we can't have the details of the experience until we do have it." [START_REF] Cage | Musicage: Cage muses on words[END_REF]182] This global representation enables another perspective of the piece. The printed score orients a natural local view. For example, in this particular case, a five-part structure is easily perceived. 3 © www.cycling74.com.

Main tool bar -2

Presents all the controls needed to calculate the events, start/stop the interface and a digital chronometer for the performance.

Pitch tuning settings -2a

This zone allows setting the "seventh tone pitch tuner" (Figure 11) parameters: the input levels, the pitch analysis type (fiddle~ by Miller Puckette, or Yin4 by Chevigné&Kawahara), the smoothing analysis settings and the reference pitch.

Page zone -3

The page zone is the main interface field. Here, the trapezoidal events (or, as in Figure 10, "real music events", showed as rectangles, in correspondence with the calculus and performance mode chosen) are displayed. A time cursor runs on a "page" whose horizontal size, in this case, is 8 minutes.

Figure 10. "Real music events" representation

The performer can choose to display, or not, the global view or the events (his own events or the partner events).

Shadow view -3a

This sub field, allows the performer to anticipate, viewing the first 90 seconds of the next "page".

Piano score strip field -4

This field displays the piano music strips from the original Cage score.

Trombone score strip field -5

This field displays the trombone music strips from the original Cage score.

Seventh tone tuner -6

This field is a display allowing the trombone player to tune, and check its tune (Figure 11). Cage asks for a particular microtonal setting, dividing a semitone in seven equal steps. The performer has to practice in order to gain facility in this aim. This part of the interface would help to train the ear and get closer to the written score.

CONCLUSIONS

As stated earlier, the modeling process is transformed in a pragmatic analysis of the musical phenomena that leads us, step by step, to model some of Cage's concepts.

We have performed Two 5 several times using conventional setting (printed parts and stop-watches). A clear preference towards minimum visual communication and good acoustical space was stated. The CAP interface, we presented, helped to get everything on the screen: the music to play, the timing, and a tuner for the microtonal control. The music was liberated from original paper pages representation and unveiling the form of the piece, hidden in its original form. Concerning the players, they can concentrate on performing when using a CAP interface. After determination of the "real musical events", in the context of "Number Pieces", they do not have to prepare any personal version, they do not need to be distracted by watching a chronometer, they do not need to loose their concentration handling paper pages or calculating start or ending times from the "time-brackets". One might wonder: when all decisions regarding the starting and ending points from events of the scores are made by a computer, what remains to be done by the performer/interpreter? The performers can ignore completely what music is being performed and just concentrate in their own performance. They can focus on the sound and silence quality required. The pianist can manage his time performance, in order that each musical event "fit" in the "real musical event" calculated, and the trombonist could be aware of his breath and tuning. In this way, the computer interface is a way to free the performers from interfering tasks, in order to get closer to Cage's original instructions. Concerning future research:

1.Investigation of other Number Pieces, and even enlarging to other Time-brackets works, such as "Music for …" series . Always taking into account the composer's instructions.

2.The interface we have developed can be easily adapted to other works. In cases of large numbers of performers, the zone giving information on the structure of the piece, could be used for musicological reasons, and switched off during a performance.

Figure 1 :

 1 Figure 1: Piano 9 th musical event

Figure 2 :

 2 Figure 2: Trombone, 6 th musical event

Figure 3 :

 3 Figure 3: Trapezoidal graphic representation of each musical strip

Figure 4 :

 4 Figure 4: A "real musical event" represented as a rectangle

1 .

 1 Cage's durations are strt 2strt 1 or end 2 -end 1 , are a kind of nominal duration Cage gives to an event. The starting time span and ending time span are equal, resulting in a paralelogram, strt 2strt 1 = end 2end 1 .

Figure 5 :

 5 Figure 5: OpenMusic Two 5 calculations steps

Figure 6 :

 6 Figure 6: Piano and trombone, time vectors translated from Cage's "time-brackets"This offline model, allowed us to, quickly, represent and evaluate a completely "indeterminate" performance.

Figure 7 :Figure 8 :

 78 Figure 7: A Two 5 version (the first half of the piece with "real music events"), represented in "OpenMusic" maquette

strt 1 ,

 1 strt 2 , end 1 , end 2 { } : are the elements from the time vector shown above, and σ (a,b): is a random uniform function that chooses a value between (a,b).

Figure 9 .

 9 Figure 9. The main interface

Figure 11 .

 11 Figure 11. Seventh-tone tuner The Cage's seventh tone concept is far from intuitive, bringing huge difficulties in the control of such demand. The performer has to practice in order to gain facility in this aim. This part of the interface would help to train the ear and get closer to the written score.

"OpenMusic" is a software developed by Ircam by Gerard Assayag, Carlos Augusto Agon and Jean Bresson. See: http://recherche.ircam.fr/equipes/repmus/OpenMusic/.

Benny Sluchin (trombone) and Sylvain Rapapport (piano) recorded this audio extracts.

The Yin algorithm was implemented in MAX/MSP by Norbert Schnell.

Actes des Journées d'Informatique Musicale (JIM 2012), Mons, Belgique, 9-11 mai 2012