Arturo Zavala-Rio

Bernard Brogliato

Dr Manuel Nava

Luis Potosn

Direct adaptive control design for one-degree-of-freedom complementary-slackness jugglers

Keywords: Complementary}slackness, Juggling, Non-smooth mechanics, Adaptive control

This note deals with the problem of controlling a simple one-degree-of-freedom (1-dof) juggling robot (a system that belongs to the class of nonsmooth hybrid complementary-slackness dynamical systems), when some physical parameters such as the object mass and the restitution coe$cient are not exactly known. The proposed adaptive controller is based on so-called dead-beat viable controllers previously studied, in which the sequence of desired `robota pre-impact velocities is suitably modi"ed. The dynamics of a simple 1-dof hopper is shown to be controllable by the proposed control algorithm. Numerical simulations support the theoretical results.

Introduction

The analysis and control of nonsmooth hybrid mechanical systems with unilateral constraints (that give rise to complementarity conditions) has recently been the object of various studies [START_REF] Ten Dam | The contact problem for linear continuous-time dynamical systems: a geometric approach[END_REF][START_REF] Van Der Schaft | The complementar-ity}slackness class of hybrid systems[END_REF], and still represents an open topic with many problems unsolved yet. In this note we focus our attention on a very simple case of such complementary}slackness systems, a one-degree-of-freedom (1-dof) juggler. This belongs to a much more general class of nonsmooth models named complementary}slackness juggling mechanical systems [START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF], that encompasses `truea jugglers as well as hoppers, nonprehensile manipulators, robots with passive dynamical environments, simple models of controlled buildings, etc. In particular it is shown that the 1-dof juggler dynamics matches with that of a (simpli"ed) 1-dof hopper. The control problem for such systems has been studied in [START_REF] Zavala-Rmh O | On the control of a one-degreeof-freedom juggling robot[END_REF] and [START_REF] Zavala-Rmh O | Commande de robots jongleurs[END_REF] where a class of hybrid dead-beat controllers has been proposed and thoroughly analyzed (see also these references for a review of juggler control). In [START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF] a more general point of view on complementary-slackness juggling systems has been taken, and some controllability criteria have been proposed. Roughly, they hinge on the analysis of an impact PoincareH map that represents the object dynamics from one impact to the next, considering the pre-impact velocity of the robot as an intermediate input. When this discrete-time map is controllable with the robot velocity as input, the object has been de"ned to be controllable via impacts. In this note, it is shown that a suitable extension of the dead-beat controllers allows one to derive an adaptive scheme which permits to relax the a priori knowledge on the object mass and on the restitution coe$cient, while guaranteeing convergence of the process state towards its desired (discrete-time) orbit.

One-degree-of-freedom juggler

Let us begin by recalling the 1-dof juggler dynamics (see Fig. 1) Oy !y *0, *0, "0, (3)

m yK "!m g# , (1)
m yK "!m g#u! , (2)
(t> I )"!e (t\ I ), ( 4
)
where the object and the robot dynamics are in ( 1) and ( 2) with u as the control input force, the complementarity conditions between the distance and the Lagrange multiplier are in (3), and the restitution law is in (4) where e3[0,1] is the restitution coe$cient. The complementarity conditions in (3) mean that all gluing or magnetic e!ects are excluded from the model, so that the contact force has to be zero whenever the distance becomes positive. On the contrary a positive contact force implies contact between the two bodies. The name complementary-slackness systems is simply taken from some standard terminology in convex analysis [START_REF] Rockafellar | Convex analysis[END_REF]. Collisions take place at impact times t I if and only if (t I

)"0 and (t\ I )(0 [START_REF] Brogliato | Nonsmooth mechanics. Models, dynamics and control[END_REF], yielding [START_REF] Zavala-Rmh O | Commande de robots jongleurs[END_REF][START_REF] Brach | Mechanical impact dynamics. Rigid body collisions[END_REF]

y (t> I )" m!e 1#m y (t\ I )# 1#e 1#m y (t\ I ), (5a)
y (t> I )" m(1#e) 1#m y (t\ I )# 1!em 1#m y (t\ I ), (5b)
where mOm /m . Subsequently in this study, f (k) will stand for f 's post-impact values f (t>

I ) ( f (t I ) if f denotes a position). Pre-impact values f (t\ I
) will be referred explicitly.

Remark 1. Let us apply Lemma 4 of [START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF] to the 1-dof juggler dynamics, i.e. consider the new coordinate system (q , q ) where q "y and q " . Then (1)}( 4) is transformed into

qK "!g#m , ( 6a
) qK "! u m #(1#m)m , ( 6b
)
q *0, *0, "0, (6c)

q (t> I )"!eq (t\ I ), ( 6d
)
where m "1/m . Now, let us consider the 1-dof hopper in Fig. 2. It is easy to show that in the coordinate system (q , q )"(y

A , y ), where y A O(m /(m #m ))y #(m / (m #m
))y , its dynamics are also modeled by ( 6) with m "1/(m #m ) and u"m g#u . Therefore, a dead-beat-algorithm-based input and impact control strategies equivalent to those to be presented in Sections 3 and 4 can be gotten for this simple 1-dof hopping robot. Let us notice that we have implicitly assumed that the bar is long enough so that y (t)'0, ∀t*0, whatever the control may be. Clearly, further studies should incorporate y !y 'R for some R'0. But then one would have to deal with possible multiple shocks, which may complicate the wellposedness of the model [START_REF] Brogliato | Nonsmooth mechanics. Models, dynamics and control[END_REF]. In [START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF], the multiple constraint case is discussed.

Dead-beat force input

The following proposition brie#y recalls the control strategy proposed in Zavala-RmH o and Brogliato (1999) (see also other references therein). It mixes a "nite-time convergent input based on the robot's controllability gramian inversion, and some logic to cope with the object's ballistic constraints. Such controllers may be seen as two-stages inputs [START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF]: the "rst stage is to design an intermediate control signal, that is the robot pre-impact velocity, whose desired value is denoted as y H (k). The second stage is the design of the control input force u. In the next section, we shall focus on an adaptive version of y H (k) that relaxes the a priori knowledge on certain physical parameters. Details on the meaning of the various terms appearing in the expression of the control input are given after Proposition 1. As pointed out in [START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF], other "nite-time inputs can be designed. In the following, the signals with upper index * denote values that the state (y , y ,y ,y ) is forced to track at all impact times. They di!er from the signals with lower index d, which denote the desired trajectory of the object. The reason for this discrepancy is that one has to incorporate the ballistic constraints of the object in the control design (the least requirement being that the intersection between the desired discrete-time orbit and the real orbit of the object, is not empty).

Proposition 1. Consider the dynamical system in (1)}(4). Suppose that the initial conditions and u are such that there exists an impact or contact time t *0. Let (y B ,y B ) be the desired position and post-impact velocity of the object. Let us dexne the following control input:

u"m g#m v, (7) v"A I (t!t I )#B I (8) with A I " 6 d I (y H (k#1)#y (k))! 12 d I (yH(k#1)!y(k)), (9)
B I "! 2 d I (y H (k#1)#2y (k)) # 6 d I (yH(k#1)!y(k)), ( 10
) d I " y (k)# (k) g , (11)
(k)"(y (k)!2g(yH(k#1)!y(k)), ( 12)

yH(k#1)" y B if h I 'y B , y(k)#r if h I )y B , ( 13
) h I " y(k)# y (k) 2g if y (k)'0, y(k) if y (k))0, (14)
∀k*0, where y(k)"y (k)"y (k) (since (k)"0), and r and y H (k#1) are chosen such that y(k)#r(h I , and

y H (k#1)'! (k), (15)
∀k*0. Then,

(1) (t)"y (t)!y (t)'0, ∀t3(t

I , t I #d I ), (2) t I> "t I #d I , (3) y(k#1)"yH(k#1), (4) y (t\ I> )"y H (k#1), ∀k*0. Moreover, if y H (k#1) is dexned as follows: y H (k#1)" 1#m 1#e y H (k#1)# m!e 1#e (k), ( 16
)
∀k*0, and

y H (k#1)" y B if h I 'y B , (y B #2g(y B !y(k)!r) if h I )y B , (17)
∀k*0, with y B '0, then,

(5) y (k#1)"y H (k#1), ∀k*0, (6) (y(k#1), y (k#1))"(y B ,y B ), ∀k*1.

Proof. See Zavala-RmH o and [START_REF] Brogliato | Nonsmooth mechanics. Models, dynamics and control[END_REF]. ᮀ

Let us provide some insights on properties (1)}( 6) of Proposition 1:

E Property 1 means that no unexpected collision takes place at any time within (t

I , t I #d I )
. This is known as the viability condition, and is very important for the overall scheme to work. In Zavala-RmH o (1997) and [START_REF] Wang | Dynamic modeling and stability analysis of mechanical systems with time-varying topologies[END_REF], more detailed and general explanations about viability and/or viability conditions can be found. These are fundamental in the study of vibro-impact systems [START_REF] Babitsky | Theory of vibro-impact systems and applications[END_REF] and have sometimes been forgotten [START_REF] Shaw | The transition to chaos in a simple mechanical system[END_REF][START_REF] Masri | On the stability of the impact damper[END_REF]. E Property 2 means that, given a collision time t I , the next impact takes place immediately after a #ight time d I . In other words, the #ight times are prede"ned at every shock through the value of d I determined by (11). This expression is such that the object never goes upwards at impact times. The term (k) in ( 12) is a calculation (according to the ballistic trajectory of the object), in absolute value, of the object pre-impact velocity at t I> , i.e. (k)""y (t\ I> )". It is calculated through yH(k#1) which in turn is chosen such that the object never be motionless at collision times (see ( 13) and ( 14)), hence (k)'0, ∀k*0 (the object always goes downwards at controlled shock times). E Property 3 means that the next impact position is arbitrarily prede"ned within the ballistic trajectory of the object through a suitable value of yH(k#1). The highest position that the object can reach during any #ight time is given by h I (see ( 14)). It would not make any sense to try to hit the object at a position that is not on its trajectory (a position higher than h I ). Eq. ( 13) assures that yH(k#1)(h I . E Property 4 means that the surface is forced to collide the object with an arbitrary pre-impact velocity through the value of y H (k#1) satisfying (15). Such condition essentially arises from the pre-impact velocity necessary condition: (t\ I> )(0. Furthermore, it appears to be fundamental in the proofs of viability and contact loss too [START_REF] Zavala-Rmh O | On the control of a one-degreeof-freedom juggling robot[END_REF].

E Property 5 means that the object post-impact velocities are arbitrarily prede"ned through the value of y H (k#1) in ( 16) (provided that ( 15) is satis"ed, which is ensured by ( 17)). E Property 6 means that the object impact PoincareH map orbit converges to the desired trajectory (y B ,y B ) after one impact.

Direct adaptive control

In this section, the signal y H ( ) ) that appears in ( 9) and ( 10) is suitably modi"ed to relax its dependence on the restitution coe$cient e (see ( 16)).

Proposition 2. Let us dexne ¸(k)Ob#(1#M) (k)# (M!b) (k)/y B
, where (k)O(2g(y B !yH(k#1)), and M is any value larger than mOm /m . Let y H (k#1) be dexned as follows (instead of ( 16)):

y H (k#1)"y B a(k)#b( (k)!y B ), ( 18
)
where y B '0 and b3(!1,!0.5). a(k) is an auxiliary state which dynamics are dexned as

a(k#1)"a(k)# c y B ( (k)!y B ) ( 19
)
with c3(b#0.5,0). Its initial conditions must be dexned according to the following criterion:

(1) If h 'y B : a( 0) is taken such that a(0)*¸(0) (and ( 19) is computed at every impact ∀k*0).

(2) If h

)y B : xrst, at k"0, a( 0) is taken such that a(0)*¸( 0) and (19) is not computed; next, at k"1, a( 1) is taken such that a(1)*¸(1) (and ( 19) is computed at every impact ∀k*1).

Then, for any e3[0,1] and m3[0, M): y(k)"y B , ∀k*2, and lim I (y (k), a(k))"(y B , aH), where aH"(1!e# 2m)/(1#e).

Before the proof of Proposition 2, let us comment on the meaning of ¸(k). The expression de"ned as ¸(k) is such that a(k)*¸(k) represents a su$cient condition (given the uncertainty of e and m) to assure h I> 'y B . This will be made clear within the proof. The importance of ensuring h I 'y B during two initial subsequent impacts will also be highlighted within the proof.

Proof. From (5a), the object dynamics integrated in time from t I to t I #d I , (11), and properties 2 and 4 of Proposition 1, we get

y (k#1)"! m!e 1#m (k)# 1#e 1#m y H (k#1) (20)
which is a valid expression for any yH(k#1)(h I and y H (k#1) satisfying condition (15). Both conditions will appear to be satis"ed later in the proof. Indeed, on the one hand, one can easily verify that the desired impact position trajectory de"ned in (13) yields, at every impact, values of yH(k#1) lower than h I (see ( 14)). On the other hand, the proposed expression for y H (k#1) in ( 18) will be proved to guarantee: y (k#1)'0, ∀k*0. Then, from (20), it follows that:

y (k#1)'0 0 y H (k#1)' m!e 1#e (k). (21)
Notice that for any m*0 and e3[0,1]: [(m!e)/(1#e)] (k)'! (k). Hence, any value of y H (k#1) greater than [(m!e)/(1#e)] (k) is even greater than ! (k). From this fact and ( 21), we have

y (k#1)'0 0 y H (k#1)' m!e 1#e (k) Ny H (k#1)'! (k),
which proves that any value or expression of y H (k#1) guaranteeing y (k#1)'0 satis"es condition (15) of Proposition 1. Now, substituting ( 18) into (20), we get

y (k#1)" y B a(k)# (k)! by B , (22)
where: O(1#e)/(1#m) and O (b#1)!1. The rest of the proof is divided in two cases depending on whether the initial conditions are such that h 'y B , or such that h )y B :

(1) Initial conditions such that h 'y B : Let us for the moment suppose that h I 'y B , ∀k*1. Then, from property 3 of Proposition 1, ( 13) and ( 12), we have y(k)"yH(k)"y B and (k)"y (k)'0, ∀k*1. Hence, Eq. ( 22) can be expressed as

(k#1)" y B a(k)# (k)! by B , ( 23
(k#1)"A (k), (24)
where

A" y B c y B 1 . ( 25
)
The origin of ( 24) is an asymptotically stable equilibrium point if the characteristic polynomial of A, i.e. P(z)" "zI!A""z#p z#p , is Schur stable (all its roots have magnitude less than unity). From (25): p "!1! and p " !c . Let us de"ne P K (s)O (s!1)P((s#1)/(s!1))"p( s#p( s#p( . We get: respectively. In the y (k) graph, the dotted-line curve represents the evolution of (k); observe that (k)"y (k)'0, ∀k*i, where i"1 if h 'y B , and i"2 if h

p( "!c , p( "2(1! #c )"2(2# (c!b!1)),
)y B . In the "rst example, Fig. 3, the following initial impact conditions were taken: y(0)"!0.2 m, y (0)" 2.5 m/s, and y (0)"1 m/s, giving h " 0.12 m'y B . The auxiliary state initial value was a(0)"!0.36"¸(0). In the second example, Fig. 4, everything was repeated except that this time the object initial impact velocity was taken as: y (0)"1.5 m/s, yielding h "!0.1 m(y B . The auxiliary state initial values were selected as: a(0)"0.43"¸(0) and a(1)"0.9"¸( 1 , ∀k*2. This suggests that conditions on the initial system impact state values and on a(0) can be found in order for the adaptive strategy in Proposition 2 to be applicable avoiding saturation of the input u when this one is bounded such that u )u)u where u (; and u ';

.

Conclusions

This note is devoted to the control of a class of nonsmooth mechanical systems, that encompasses simple models of juggling and hopping robots. Its aim is to extend some previously studied control algorithms [START_REF] Zavala-Rmh O | On the control of a one-degreeof-freedom juggling robot[END_REF][START_REF] Brogliato | On the control of complement-ary}slackness juggling mechanical systems[END_REF]. Roughly speaking, such controllers are constructed by "rst designing a sequence of "ctitious inputs in terms of the `robota pre-impact velocities (which constitutes a step that has attracted the interest of some researchers in the "eld [START_REF] Buehler | Planning and control of robotic juggling and catching tasks[END_REF]). Then in a second stage, one designs the force control input that guarantees that this pre-impact velocities sequence is realized. The note focuses mainly on the "rst step. It concerns the relaxation of the a priori knowledge of physical parameters like the kinematic restitution coe$cient e and the object's mass, in the design of the robot pre-impact velocities. A semi-globally stable adaptive scheme is proposed. Some numerical simulations illustrate the theoretical results.

Fig. 1 .

 1 Fig. 1. One-dof juggler.

Fig. 3 .

 3 Fig. 3. Adaptive control: h 'y B .

  ). Observe that in both examples, y (k) and a(k) converge asymptotically towards y B and aH respectively, and y(k)"y B , ∀k*2 (∀k*1 if h 'y B ). Finally, let us point out an important observation concerning the upper and lower dotted lines in the force curves. These stand respectively for ; !3#e!2m# 2em)/(1#e)]g and < O [(3!2e#4m!em)/(1#e)]g. In (Zavala-RmH o & Brogliato, 1999), a control strategy ensuring the convergence of the object impact states to the desired "xed point avoiding saturation of the input u when this one is bounded such that u )observed in the present examples, Figs. 3 and 4, show that the lowest and highest values of u at each #ight time,

 'y B.

and p( "2#2 !c " (2#2b!c). It is well-known that if P K (s) preserves the same degree as P(z), i.e. p( O0, then P(z) is Schur stable if and only if P K (s) is Hurwitz stable (all its roots have negative real part) [START_REF] Bhattacharyya | Robust control. The parametric approach[END_REF]. One can easily verify that for any m3[0, M), e3[0,1], b3(!1,!0.5), and c3(b#0.5,0), we have: p( G '0, ∀i"0,1,2, which is a su$cient condition for P K (s) to be a second degree Hurwitz stable polynomial. Therefore, the proposed tuning criterion, i.e. b3(!1,!0.5) and c3(b#0.5,0), ensures the Schur stability of P(z), guaranteeing the asymptotic stability of (24), hence lim I (k)"0.

(3)'0. The whole process is then repeated at every impact, proving that y (k#1)'0, ∀k*0. Therefore h I 'y B , ∀k*1, which completes the proof (for the present case).

(2) Initial conditions such that h )y B : From the preceding analysis, one can easily realize that in this situation, by just ensuring h 'y B and subsequently h 'y B , the asymptotically stable second order dynamics of (k) in ( 26) is retrieved ∀k*1, and consequently: lim I (k)"0, and y(k)"yH(k)"y B , ∀k*2. Then, all we need is to show that this is accomplished through the choices of a(0) and a(1). Recalling that M'(m!e)/ (1#e) for any m3[0, M) and e3[0,1], and since a( 0

, we have:

Hence y (1)' (0) (see ( 22))Ny(1)#y (1)/2g'y B (recall the de"nition of (k) and property 3). Therefore The following numerical examples show the results obtained from the application of the proposed adaptive scheme to a 1-dof juggler with the following parameter values: e"0.8, m "0.1 kg, and m "1 kg, giving m"0.1. The desired xxed-point is (y B ,y B )"(0,3.13 m/s), resulting in a "xed apex h B "y B #y B /2g"0.5 m. The control parameter values were taken as b"!0.9, c"!0.3, and M"0.2. Figs. 3 and4 show the results of the simulations for the two initial condition cases: h 'y B and h )y B , respectively. In the left-hand side of the "gures, the position trajectories and the control input u are presented. In the system trajectory curves, the lower and upper dashed lines indicate respectively the values of y B and h B , while that in the input force graphs indicates the robot weight (m g). The meaning of the dotted lines appearing in the force curves will be explained later. In the right-hand side of the "gures, the discrete evolution of


Jonathan Bell
email: jonathan.bell@univ-amu.fr

The Risset Cycle, Recent Use Cases With SmartVox

The "In memoriam Jean-Claude Risset" cycle of compositions marks a significant turn in the evolution of SmartVox: initially designed as a rehearsal and performance tool for choirs in which singers received their score and audioguides through their smartphones' browser, SmartVox can now be used in more diversified setups, from large ensembles with soloists and choir to small instrumental chamber music groups with players wearing head-mounted displays, in participative concerts with audience interaction, or in staged operatic contexts. This paper first situates Smart-Vox among various technologies of distributed animated notation, and then discusses four pieces extracted from the 'Risset Cycle', to all be performed with this technology (a form of computer-aided "conductor-free" performance). From a compositional point of view, these works were conceived as spectral mimetic transcriptions of synthesized sounds, as a tribute to the French pioneer of digital sound synthesis and co-founder of the spectral school. Spectral music as a compositional aesthetic emerged simultaneously with the birth of the digital era in the 1970s. Through a neo-spectral approach to music, this paper seeks to make a case for a compositional ideal (the mimetic transfer of a natural/synthesized sound to the instrumental/vocal domain) which today's technologies have made more realistic.

INTRODUCTION: MIMESIS

If mimesis was a governing principle of artistic creation in Ancient Greece, it was most certainly also at the heart of the French spectral music's project of the 1970s. In this context indeed, composers rarely put into question why for instance the faithful imitation of the harmonic spectrum of a bell sound qualified as art. Assuming that harmony in music is paramount, one can now examine how, in the case of singers for instance, this mimetic transfer might be facilitated when one receives an audio-score [1] through his/her ear, reproducing microtonal harmonies by just imitating the perceived pitch (as is the case with SmartVox). In this case the (auditory) notation closely resembles the desired effect. However, the philosopher Nelson Goodman demonstrated that this is not necessarily the case with musical notation: in fact even beyond the musical realm, he is famous for showing that one thing need not resemble another in order

for that other to represent it. Working on real-time animated music notation and virtual reality [START_REF] Carey | SpectraScore VR: Networkable virtual reality software tools for real-time composition and performance[END_REF], the composer Benedict Carey reminds us of an essential aspect of musical notation: 'the closer a musical unit gets to representing a direct action (that is, the movement of an object in space) the more mimetic it becomes.' [START_REF]From Mimetics to Memetics[END_REF] This observation highlights the great complexity of rhythmic notation in common practice musical notation, when compared to modern video game-like notations such as, for instance, Digital Audio Workstations where a cursor scrolls from left to right, or in Guitar Hero and modern piano roll-notation, where notes or tablature fall from top to bottom of the screen. On the contrary, in traditional music notation, the historically inherited practice of the arithmetic division of tuplets, their fitting into bars and beats, and the constant adjustments instrumentalists have to make to coordinate with the gestures of a conductor show all together how mimetic representations are-for better or worse-much easier to understand for beginners than the culturally inherited common practice.

NOTATION

Creative use of Technology for Musical Notation: Global Context

Ryan Ross Smith's animatednotation.com website demonstrates that today many composers find fixed common practice notation limiting. To solve this issue, attendees of the Tenor Conference1 have proposed elements of response. With Kagel's Prima Vista (1962/64) setting a major precent, animated notation often relies on a large screen projecting the parts, as most famously exemplified in Smith's compositional practice. The score can therefore be seen by the performers but also by the audience, thus making notation part of the theatrical performance.

Other performance-oriented systems (SmartVox [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF] [5], Zscore [START_REF] Zagorac | ZScore: A Distributed System For Integrated Mixed Music Composition and Performance[END_REF], Decibel [START_REF] Hope | Scoring an Animated Notation Opera -The Decibel Score Player and the Role of the Digital Copyist in 'Speechless[END_REF] [START_REF] Hope | The DECIBEL Scoreplayer -A Digital Tool for Reading Graphic Notation[END_REF], Maxscore [START_REF] Hajdu | MaxScore: Recent Developments[END_REF], comprovisador [START_REF] Louzeiro | Improving Sight-Reading Skills through Dynamic Notation -the Case of Comprovisador[END_REF]) endeavor to distribute and synchronize each part of the score on the performer's devices (whether Smartphones, tablets or laptops). With SmartVox for instance, rendering the score in the browser directly revealed itself to be very effective for this kind of setup. Thanks to cross-platform web technologies, the application works with any browser capable device, and no installation is required by the client. The node.js2 /websocket architecture of SmartVox will hopefully inspire more composers, researchers and developers to investigate the emerging musical practice of distributed notation.

Graphical Notation in Bach

Most pieces performed with SmartVox rely highly on Bach [START_REF] Agostini | BACH: an environment for computer-aided composition in Max[END_REF], a realtime computer-aided composition package for Max/MSP. The use of color and shape in pieces like In Memoriam JC Risset 1 or Mit Allen Augen (In memoriam JC Risset 2) was inspired by Cat Hope [START_REF] Hope | Electronic Scores for Music: The Possibilities of Animated Notation[END_REF] and Lyndsey Vickery [START_REF] Vickery | Some Approaches to Representing Sound with Colour and Shape[END_REF], two active composers, researchers, developers of the Decibel ScorePlayer [START_REF] Hope | The DECIBEL Scoreplayer -A Digital Tool for Reading Graphic Notation[END_REF], whose approach to animated graphical notation opens new territories for musical scores today.

Unlike other notation packages in Max (MaxScore [START_REF] Hajdu | MaxScore: Recent Developments[END_REF], or the Symbolist [START_REF] Gottfried | Symbolist: An Open Authoring Environment for User-Defined Symbolic Notation[END_REF]) which were imagined as symbolic representations in the first place (Rama Gottfried describes the Symbolist as a version of adobe illustrator in Max), the Bach environment emerged from Open Music [START_REF] Bresson | OpenMusic -Visual Programming Environment for Music Composition, Analysis and Research[END_REF] and computer-aided composition, which explains some of its limitations from a graphical point of view: for instance, it is impossible to insert a picture in a bach.roll (in proportional notation), and the bach.roll object does not support articulations (unlike the bach.score object in bars and beats notation). However, one can get around this graphical limitation by adjusting the duration line settings (see Figure 1). The use of colors is also easily customizable with the help of 'slots'. In spite of its few display limitations, one of the strengths of Bach consists of its ability to control synthesizers from the notation directly. Slots can therefore be understood as metadata or temporal automations that can subsequently be mapped onto any Max-programmed synthesizers, enabling staves of a score to be manipulated as tracks of a DAW 3 .

Distributed Musical Notation

Composers and researchers increasingly acknowledge the strong analogy which can be drawn between the traditional 'score and parts' musical practice led by a conductor, and the modern distributed systems or web applications (Zscore [START_REF] Zagorac | ZScore: A Distributed System For Integrated Mixed Music Composition and Performance[END_REF] -MASD [START_REF] Nathan | Musician Assistance and Score Distribution (MASD)[END_REF] -SmartVox [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF]), in which multiple clients coordinate their actions by passing messages to one another.

The Tenor 2018 conference in Montreal revealed to the author an interesting similarity between the Decibel Score-Player and SmartVox, in the sense that the two softwares are rather elementary solutions both converging towards the score player performance-oriented paradigm, whilst other notation packages (Bach, Maxscore, Symbolist...) were also designed for more elaborate computer-aided composition and real-time processes. Although the Decibel ScorePlayer is today's most reliable iOS application solution for distributed animated notation, Cat Hope and Aaron Wyatt have evoked the possibility to migrate their system to the browser, for instant access over the internet presumably, but also optimization of networking issues, and cheaper 3 see https://youtu.be/s4qS2khwkT0 for demonstration.

production cost in local settings-e.g. for projects involving over fifty devices, the iPad becomes a very expensive solution). The most likely architecture to allow this transfer of technology would be a node.js server4 (server-side javascript), with the WebSocket communication protocol, a solution used by SmartVox as early as 2015, thanks to Norbert Schnell and Benjamin Matuszewski from IRCAM in Paris. SmartVox sends and synchronises mp4 audiovisual scores, which has demonstrated undeniable robustness in large scale concerts and rehearsals, but also reveals the potential weakness of a 'non-realtime' solution (as a sort of fixed multichannel tape) in which performances of the piece would be similar each time. Other composers/researchers (Georg Hajdu, Rama Gottfried, Slavko Zagorac) are currently investigating forward thinking solutions which will allow the control of SVG (Scalable Vector Graphic) directly on the client-side HTML page. The architecture chosen for this by Georg Hajdu and Rama Gottfried is node.js, sending osc over WebSockets. This project will result in a realtime distributed 144-parts site-specific composition in Hamburg in May 2019.

Augmented Reality Distributed Notation

In Memoriam JC Risset 15 , premiered in September 2018 at the Gaudeamus Festival (Utrecht), constitutes the author's first experiment using head-mounted displays. By simply displaying each part of the score over the heads of the performers (for flute and clarinet only), this piece has revealed interesting potentials to be exploited in future works.

Just as traditional scores placed on a music stand, screenscores displayed on a tablet (for instrumentalists) or on a phone (for singers) oblige musicians to look and orientate their body constantly in the direction of the score. This well-established convention of the classical concert setup considerably limits the possibilities of staging music, in a theatrical context for instance. In such cases as the Ictus Ensemble's interpretation of Vortex Temporum by Gérard Grisey 6 , where the musicians had to learn the score by heart, and perform without a conductor, Wi-Fisynchronized head-mounted displays might be an interesting way to help musicians coordinate in time and space, while moving on stage or around the audience, without insurmountable performance challenges.

According to the performers' feedback, head-mounted setups provide a large and comfortable display, since the environment is still visible around the score (see Figure 2), or through the score in the case of holographic display (such as the Aryzon headset for instance). The performers also showed interest in their ability to move freely on stage or elsewhere (the piece was choreographed differently according to the venue: in a church, the flute and clarinet started the piece behind the audience and gradually approached the altar), which relates to the term phygital (physical+digital) coined by Fabrizio Lamberti [START_REF] Lupetti | Phygital play HRI in a new gaming scenario[END_REF], who claims that with AR and VR, the possibilities of physicalization of gaming will soon encompass other fields. While awaiting more discrete (such as Google glasses, which would invisible from an audience's point of view) but still affordable solution, AR opens vast domains for further research, which could go far beyond the mere display of animated notation. However, important questions then arise regarding what would be pertinent to achieve with such technology: in a VR context for instance, with a player on stage, how can the limitation due to the destabilization of the performer's proprioception be overcome? Also, now that any form of immersive score can be prototyped, 7 how would this be of musical interest, and how could this have a convincing musical impact on the compositional/performative outcome? SmartVox, for instance, delivers and synchronizes mp4 files, and should soon support 360-degree videos 8 , but how can this benefit the performer in a musical sense? Australia holds today the world's largest community of composers/researchers working in animated notation, and Australian composers such as Benedict Carey [START_REF] Carey | SpectraScore VR: Networkable virtual reality software tools for real-time composition and performance[END_REF] and David Kim Boyle [START_REF] Kim-Boyle | The 3-D score[END_REF], who specifically investigate 3D-scores in VR environments, should soon bring elements of response to this issue.

NETWORKED MUSICAL PERFORMANCES -NMPS

3.1 SmartVox.eu, Score Distribution over the Web and Remote NMPs

With the exponential growth of the web, hosting SmartVox 9 on the internet (i.e. on a remote server rather than a local one) appeared as a necessity. However we demonstrated (in Chapter 4.2 'Measurements of timing accuracy' [START_REF] Bell | AUDIOVISUAL SCORES AND PARTS SYNCHRONIZED OVER THE WEB[END_REF]) that, although the synchronization of different parts was quite accurate in this way, local solutions remained safer (in the same room, over Wi-Fi). Also, notwithstanding the fact that SmartVox undoubtedly belongs to the realm of Networked Music Performances, it became clear that its practical application falls under the 'local NPMs' sub-category defined by Gabrielli and Squartini [START_REF] Gabrielli | Wireless Networked Music Performance[END_REF].

Since the advent of the internet, thorough research has 7 Such as the ones imagined by Mauricio Kagel's film Ludwig Van (1969), see for instance: https://youtu.be/7l8vPWFIgxI?t=1591 8 This could be done by simply implementing a 360 mediaplayer in HTML5, e.g.: https://bitmovin.com/demos/vr-360 9 Each instrumental/vocal part of the piece And the Sea is accessible through the following url www.smartvox.eu, and can be accessed simultaneously from e.g., an iPad for the flute, Android tablets for piano and cello, and a phone for the singer. A trailer of the premiere of the piece is accessible here: https://youtu.be/prcXUbhd-ZY been undertaken in the realm of remote Networked Musical Performances (NMP) [START_REF] Rottondi | An Overview on Networked Music Performance Technologies[END_REF]. Today however, local NMPs still seem today more viable, both technically and artistically speaking. While young generations tend to play video games online (i.e. remotely), with friend avatars or anonymous players most often around the globe, many examples would show that musicians still feel more enclined to the idea of reading a score or improvising together in the same room. In Embodiment and Disembodiment in Networked Music Performance [START_REF] Hajdu | Embodiment and disembodiment in networked music performance[END_REF] Georg Hajdu explains that "appreciation [of the musical experience] relies on the plausibility between physical action and sonic result." Since the emergeance of NMPs,10 some disappointment arose from the fact that, from the audience's point of view (but also for the musicians themselves), very little can be seen and therefore understood, which worsens with distant performers: "Because of the remoteness of the participants, these actions may not always be perceived directly or immediately [...], classical cause-and-effect relationships [...] are replaced by plausibility, that is the amount to which performers and spectators are capable of 'buying' the outcome of a performance by building mental maps of the interaction. In NMP, this can be facilitated by the use of avatars, projected visually, and carefully orchestrated dramaturgies, involving participants in game-like scenarios." Many VR environments today focus on this interaction between a physical action and its sonic result. New Atlantis ( [START_REF] Sinclair | New Atlantis: Audio Experimentation in a Shared Online World[END_REF]), for instance, is a multi-user sound exploration platform in which several players can interact with each other. 11 With their ability to represent avatars of musical performers, these new interfaces may soon have the ability to recreate the visual entity producing sound (or music). By recreating virtual causal links between an action and its sonic result, these online game interfaces should provide users with the missing visual element that prevent NPMs from becoming a genuine globalized musical practice.

The 'SmartBox', a Raspberry Pi Hardware Embedded System Solution for Local NMPs

The author has shown evidence that SmartVox is suitable for large scale projects such as le temps des nuages 12 in which eighty singers and musicians had their score synchronized through the same network [START_REF] Bell | AUDIOVISUAL SCORES AND PARTS SYNCHRONIZED OVER THE WEB[END_REF]. These productions still enjoy an increasing interest from choirs and ensembles, 13 requiring a very modest technical setup (only one Wi-Fi access point, e.g. Ubiquiti Unifi) for choirs up to thirty singers, with a node.js server running on a Mac computer. However, in the more intimate context of chamber music (as in In Memoriam JC Risset 1), the focus is slightly different: the network load is much lighter, which encouraged finding a minimal hardware solution, in order to make possible rehearsals without the physical presence of the composer or the mobilization of a technician only to setup a network. Installing the server on the performer's computer remotely has often been successful with musicians unfamiliar with technology, thanks to the flexibility of the Node Package Manager (NPM), which reduces the installation of SmartVox to a few command lines. 14 This installation process nevertheless remained an obstacle for the dissemination of SmartVox. In search of a light plugand-play dedicated system to be sent over the post, the Raspberry Pi quickly appeared as the best option to host SmartVox on an embedded system. Node.js runs on Raspbian, and SmartVox proved to be very stable on a Raspberry Pi 3, so, once installed, the only two steps for a 0-conf deliverable hardware were:

• Setting up a static address for a dedicated router (e.g. tp-link...). • Starting SmartVox at boot.

Starting a script at boot can be done on Raspbian with a file containing the following in the etc/systemd/system:

[ U n i t ] D e s c r i p t i o n =My s e r v i c e [ S e r v i c e ] E x e c S t a r t = / home / p i / D e s k t o p / h e l l o . s h [ I n s t a l l ] WantedBy= m u l t i-u s e r . t a r g e t

With the hello.sh script containing the following to launch the server:

# ! / b n / b a s h cd / home / p i / D

e s k t o p / r i s s e t npm r u n s t a r t e x e c b a s h

This low-cost system (less than 65 C, for a Raspberry and a router) now allows the sending of ready-to-use scores. Once the system is power-supplied, all the performers need to do is to join the dedicated Wi-Fi, and type the static IP address of the server on their smartphone/tablet (i.e. for the performers: 192.168.0.100:8000, and for the conductor: 192.168.0.100:8000/conductor). In January 2019, the system was rented to the Caen French conservatoire via Ba-belScores 15 , thus proposing a rental of performing scores (separate parts) of a new kind.

The Raspberry Pi was interestingly used for score rendering by the Troy-based composer Kelly Fox, for the performance of his piece Accretion [START_REF] Fox | Accretion: Flexible, Networked Animated Music Notation For Orchestra With the Raspberry Pi[END_REF]: "the paper seeks to make a case for adopting the Raspberry Pi as a powerful device and method of distribution/performance of Animated Music Notation'. Unlike SmartVox, in which the Raspberry Pi is used to launch a node.js server." Fox's approach proposes to use several Raspberry Pies as notation rendering clients.

MIMETIC ORCHESTRATION

With the exception of the first opus (In Memoriam JC Risset 1), whose pitch material was extracted from the analysis of FM synthesis spectra, all the pieces of this cycle constitute mimetic (a term attributed to Lindsay Vickery [START_REF] Vickery | Hybrid Real/Mimetic Sound Works[END_REF] and Benedict Carey [START_REF]From Mimetics to Memetics[END_REF]) orchestrations of the PRISM laboratory synthesizer, developed by Richard Kronland-Martinet [START_REF] Conan | An Intuitive Synthesizer of Continuous-Interaction Sounds: Rubbing, Scratching, and Rolling[END_REF], who worked for thirty years with Jean-Claude Risset at LMA, Marseille, France.

This synthesizer is based on a perceptive model (as opposed to a physical model [START_REF] Ellis | Modalys demonstration[END_REF]) and carries the influence of Risset's exploration of timbre synthesis, examined through the perspective of human perception [START_REF] Risset | Exploration of timbre by analysis and synthesis[END_REF]. The great majority of the electronics in other pieces of the cycle (In Memoriam 2, 3 and 4) makes extensive use of the liquefaction parameter, which turns a continuous sound into small grains evoking the resounding impacts of drops on multiple resonant metallic surfaces, or some form of imaginary rain on metallic chimes. 16 The Bach library was again very helpful for musical transcription, subsequently allowing for transfer to the instrumental domain.

Benedict Carey's doctoral thesis 'Between Mimetics and Memetics' examines the credo assumed by various spectral composers, for whom the very act of compositing was sometimes almost equivalent to the ability to orchestrate or translate sounds to the instrumental domain. Classical contemporary music scenes such as those represented in Europe in Gaudeamus or Darmstadt academies and festivals reveal, however, that such preoccupations are often today very far from what the young generations of composers wish to express. Therefore, one can only talk of neo or postspectralism when referring to such techniques. Whilst still taught in institutions like IRCAM, or briefly mentioned as part of the undergraduate composition curricula, one can deplore the fact that this aesthetic canon has seen its day now that technologies (such as the tools presented in the present paper) finally allow more intuitive and user-friendly interfaces to the composer (Bach, Ableton, PRISM synthesizer), auditory and visual computer assistance for microtonal intonation and synchronization adjustments to the performer (SmartVox), and thus probably more convincing results from an audience's point of view.

Time Domain: Temporal Precision and Mimetic Transfer

At IRCAM in January 2018, Benjamin Matuszewski highly improved the synchronization possibilities of SmartVox by implementing a client-side algorithm that puts back in sync devices whose drift exceeds a certain threshold ( [5], Chapter 4.3). Until this new release, SmartVox had to deal with a more approximate temporality, but it can now explore a wide range of tightly synchronized musical situations, between musicians, electronics and video for instance.

In none-pulsed music, in spite of the great conducting tradition in chamber music and orchestral works, left-to-right scrolling cursors distributed on the performers' devices (as in the Decibel ScorePlayer or SmartVox) seem a far more straightforward strategy to obtain tight synchronization rather than the bars and beats 'encoding' (quantification by the composer with or without the help of algorithms) and decoding processes (a compromised interpretation by the instrumentalist, between the rhythmic values written on the page and the gestures of the conductor), inherited from a scoring tradition in which a regular meter was assumed.

The bach.roll object displays notation in proportional time, and outputs notifications of its playback status in real-time. 16 A liquefation demonstration is available here: https://youtu.be/2kdIaqAhUGs

These notifications can be interpreted in Max For Live in order to synchronize 1/ the notation for human players in Bach and 2/ the electronics in Ableton Live. Figure 3 shows how Ableton's playback controls can be accessed through the live-set path of the live object model (LOM), which makes constant back and forth playbacks possible between the score and the electronics, during the compositional process. This interface facilitated the composition of Mit Allen Augen, In Memoriam J.-C. Risset 2, a piece involving large forces to be performed in Paris in March 2019 (12 voices, 12 instruments and electronics).17 Pieces of the Risset cycle all benefit from this improvement: in the first piece of the cycle, a passage is based on rhythmical games between performers, taking advantage of the cursor-type display of time. 18 In Das Hoheslied, In Memoriam Jean-Claude Risset 3, to be premiered in June 2019, students of HfMT Hamburg were able to sight-sing (for the very first time) passages which strikingly resembled the target model. 19 In the Pocket Opera similarly, voices should be able to match the attack of the tape with great accuracy. 20

Frequency Domain: Harmonic Analysis of Frequency Modulation

Rather than citing the oft-used Shepard-Risset glissando illusion, the author found it more appropriate to re-activate one of the most successful techniques of the beginning of computer music: frequency modulation, which Risset was amongst the first composers to use in his piece Mutations (1969), thanks to Chowning's generous permission. This is why nearly all the harmonic material from In Memoriam J.C. Risset 1 and 3 was generated by FM synthesis.

For frequency analysis, although Iana [START_REF] Todoroff | IANA: A Real-Time Environment for Analysis and Extraction of Frequency Components of Complex Orchestral Sounds and its Application within a Musical Realization[END_REF] was formerly used (and also favored by Daniele Ghisi [START_REF] Agostini | BACH: an environment for computer-aided composition in Max[END_REF] in some of his transcription patches), the zsa.freqpeak descriptor [START_REF] Malt | Zsa.Descriptors: a library for real-time descriptors analysis[END_REF] offered seemingly more accurate results. A Max For Live device was built for pitch visualization purposes. 21As a reference to Risset's findings regarding the temporal evolution of the harmonic content of digitally recorded trumpet sounds (which becomes richer in high frequency harmonic when loudness increases [START_REF] Risset | Computer Study of Trumpet Tones[END_REF], the evolution of frequency's 'Modulation index' 22 , was orchestrated by successive entries of voices, from the lowest register (bass) to the highest (soprano). 23

Conclusion on Mimetic Spectralism and Vocal Imitation

Some of the tools presented in this chapter show that the possibilities offered by today's technologies would have appealed to the supporters of the 'mimetic spectralism' imagined in the 1970s. If the compositional aesthetics followed by these composers is not to everyone's taste, they may at least provide a fertile ground for artistic/scientific research, because their aims and methods, concerned with the reproducibility of a model, are suitable to measurements and, for instance, quantifiable assessments. 24 In a more scientific context, members of the PRISM 25 laboratory undertook an experimental study of vocal imitation which recalls the sight-reading experiment in Das Hoheslied. According to the author, Thomas Bordonné, this study "aimed at determining the main characteristics of sounds used by participants during vocal imitations". Bordonné, concludes: "Vocal imitations seem to be a good tool to access the perception and determine which aspects of the sounds are relevant" [START_REF] Bordonné | Assessing sound perception through vocal imitations of sounds that evoke movements and materials[END_REF]. In this setup, therefore, the spontaneous vocal response of participants could be interpreted in similar ways to the SmartVox-led reading sessions in which the singers are asked to imitate what they hear.

CASE STUDY: THE POCKET OPERA, COLORS AS A METAPHOR FOR HARMONY IN PARTICIPATIVE SETTINGS

Participation

Productions based on SmartVox have highly taken advantage of the emergence of participative concerts, in which local community choirs or students get an opportunity to sing with professional musicians (e.g. SmartVox or Le temps des Nuages). Like SmartVox, the web application Your Smartest Choice 26 (dedicated to a concert piece of the same name by Huihui Cheng) was developed by Benjamin Matuszewski at IR-CAM, in the SoundWorks frameworks [START_REF] Schnell | Soundworks -A playground for artists and developers to create collaborative mobile web performances[END_REF]. In this piece, the audience interacts with the performers on stage through a video game running in the browser of their smartphone. This project encouraged the author to take this participative aspect even further, not only with singers of various levels joining professionals in a production (as in SmartVox or Le temps des Nuages), but also with the audience participating in the performance, through a video game deployed over Wi-Fi, accessible through their own smartphone, just like the performers' scores.

Chroma, the Relationship Between Pitch and color

The pocket opera project (In Memoriam J.C. Risset 4) consists in a staged work in which professional musicians (the De Caelis ensemble) will interact with secondary school choirs (singing) and with the audience (playing). The pedagogical interest here consists of familiarizing the students with notions of tuning, intonation and harmony. As in most SmartVox projects, the personalized in-ear guide tones will help the choral students to sing in tune, but this time the audience will also be asked to follow the musical action happening on stage. The full score is projected on a screen and the game displays balloons of different colors scrolling on the phone. Each color corresponds to a specific pitch/sound, in order to prompt audience members to follow the score and click on the matching color. A didactic introduction will explain the rules of the game. 27Reflecting again on questions raised by Lyndsey Vickery [START_REF] Vickery | Some Approaches to Representing Sound with Colour and Shape[END_REF] regarding the possible roles of color in musical notation, and taking his findings to a musical language more focused on pitch and harmony, color was used for its harmonic significance, remembering that the Ancient Greek word for color (chroma) interestingly led to chromaticism. With all harmonic fields generated from liquefied sounds of the PRISM synthesizer [START_REF] Conan | An Intuitive Synthesizer of Continuous-Interaction Sounds: Rubbing, Scratching, and Rolling[END_REF], the pocket opera project 28(in memoriam J.C. Risset 4) seeks to develop, through a process of gamification of musical notation, an awareness to notions of pitch and spectral harmony among audiences of all backgrounds.

CONCLUSION

Initially conceived almost exclusively as a rehearsal tool for choral practices [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF] [START_REF] Bell | AUDIOVISUAL SCORES AND PARTS SYNCHRONIZED OVER THE WEB[END_REF], recent use cases have shown that SmartVox is in fact better described as a distributed score player suitable for instruments as well as vocalists with or without electronics. If notation remains a key concept for SmartVox, the notion of Networked Musical Performance probably defines it more specifically. Its recent synchronizing capabilities make it well-suited for mimetic spectral music, in which the rhythmic and harmonic characteristics of a recorded sound serve a as basis for composition and orchestration.

Figure 1 .

 1 Figure 1. Duration line adjustment in Bach.

Figure 2 .

 2 Figure 2. Score display from the performer's point of view.

Figure 3 .

 3 Figure 3. Max For Live device syncing Bach and Ableton.

http://www.tenor-conference.org/

Server-side JavaScript, see: https://nodejs.org/en/

According to a private email conversation with the developper Aaron Wyatt.

A recording of the piece is available at the following address: https://youtu.be/hQtyu1dcCaI

See: https://youtu.be/JFvrYy6EeWE

The American computer music network band 'the Hub', formed in 1986, contributed to the popularization of this new genre.

Towards the end of the following extract, three players can be observed producing sounds together: https://vimeo.com/264626943

A recording of the piece is available at the following address: https://youtu.be/SyFdR2HiF00

SmartVox was used for the rehearsals and performance of To See The Invisible, an opera by Emily Howard, Aldeburgh, Snape Maltings 2018https://snapemaltings.co.uk/concerts-history/aldeburgh-festival-2018/to-see-the-invisible/

SmartVox is open source and ready to dowload on GitHub: https://github.com/belljonathan50/SmartVox0.1.

Babelscores (https://www.babelscores.com/) is an online score database for classical contemporary music, currently actively supporting the SmartVox project: http://1uh2.mj.am/nl2/1uh2/lgi4u.html.

The following example shows the convenience of the Bach/Ableton inter-application communication https://youtu.be/VJvY5wYl cM

A rhythmical passage in In Memoriam Jean-Claude Risset 1 https://youtu.be/hQtyu1dcCaI?t=349

A Target sound is followed by its imitation by the choir in a sightreading session of Das Hoheslied, In Memoriam Jean-Claude Risset 3 https://youtu.be/EHYq9nFF6sE

[START_REF] Rottondi | An Overview on Networked Music Performance Technologies[END_REF] The harmonic/rhythmic contour of the electronics, once transcribed with the help of Bach, is then distributed to different voices in hoquet-like sort of games: https://youtu.be/eBshi

2F20k[START_REF] Hajdu | Embodiment and disembodiment in networked music performance[END_REF] Real-time spectral analysis with Bach and Zsa.FreqPeak

https://youtu.be/D6mCgx4pSxs[START_REF] Sinclair | New Atlantis: Audio Experimentation in a Shared Online World[END_REF] See https://youtu.be/OnT-Zgkh5MA for demo purposes.[START_REF] Fox | Accretion: Flexible, Networked Animated Music Notation For Orchestra With the Raspberry Pi[END_REF] See https://youtu.be/sgSjIpSD8yQ.[START_REF] Vickery | Hybrid Real/Mimetic Sound Works[END_REF] As, for instance, in the aforementioned Hambourg's choir sightreading example: Das Hoheslied, In Memoriam Jean-Claude Risset 3.25 https://www.prism.cnrs.fr/[START_REF] Ellis | Modalys demonstration[END_REF] Your Smartest Choice, by composer Huihui Cheng, is an IRCAM-Eclat Festival joined production in which the audience interacts with the performers through their smartphones. http://cosima.IRCAM.fr/2017/02/05/your-smartest-choice-eclat-festival/ The piece was subsequently performed at the Luxembourg Rainy Days Festival, the code for the game is available here: https://github.com/IRCAM-cosima/your-smartest-choice

The piece starts with an explanation of the game's principal: https://youtu.be/s-VSs3TcqLk), it then explores various possibilities with the system (https://youtu.be/p4tT1CQGf-A)

A description of the project is available at the following address: https://www.decaelis.fr

Acknowledgments

I would like to thank Georg Hajdu, Daniele Ghisi, Benjamin Matuszewski and Richard Kronland-Martinet.


Jonathan Bell
email: jonathan.bell@univ-amu.fr

Benedict Eris Carey
email: benedict.carey@hfmt-hamburg.de

Benedict Eris

Carey Animated

ANIMATED NOTATION, SCORE DISTRIBUTION AND AR-VR ENVIRONMENTS FOR SPECTRAL MIMETIC TRANSFER IN MUSIC COMPOSITION

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

other in order for that "other" to represent it. Working on real-time animated music notation and virtual reality [START_REF] Carey | Spectrascore vr: Networkable virtual reality software tools for real-time composition and performance[END_REF], the author has remarked in the past of an essential aspect of musical notation: 'the closer a musical unit gets to representing a direct action (that is, the movement of an object in space) the more mimetic it becomes.' [START_REF]From mimetics to memetics[END_REF] This observation highlights the great complexity of rhythmic notation in common practice musical notation, when compared to modern video game-like notations such as, for instance, Digital Audio Workstations where a cursor scrolls from left to right, or in the popular arcade and video game Guitar Hero and modern piano-roll notation, where notes or tablature fall from top to bottom of the screen (a practice known as animated notation). In traditional western music notation on the contrary, the historically inherited practice of the arithmetic division of tuplets, their distribution into bars and beats, and the constant adjustments instrumentalists must make to coordinate with the gestures of a conductor, show as a whole how mimetic representations are-for better or worse-much easier to understand for beginners than the culturally inherited memetic (i.e. symbolic) common practice.

MIMETICS VS MEMETICS

The Memetic Nature of Animated Notation

When we score music by hand, we do so to varying degrees of mimetic accuracy, albeit often without reference to essential extra-musical information required to interpret the music, we are heavily engaged in a memetic process. The authors propose that an animated score can be described, in some part, by where it exists in terms of its mimeticness and its memeticness. Guitar tablature, and Guitar Hero make use of very mimetic forms of notation. That is, notation which very closely related to the (prescribed) action to be performed, and less bound by the semiotic or memetic information one finds in common practice notation, which imply abstract representations engaged with descriptions of the "end-result" sound, allowing for a wider range of possible interpretations, more so with graphic notation, and even more so in more abstract forms of animated notation. The authors believe that Mimetics is therefore a useful term for the field scores which rely on imitation, to convey their desire for audification (a term attributable to Lindsay Vickery [START_REF] Vickery | Hybrid real/mimetic sound works[END_REF] and the author [START_REF]From mimetics to memetics[END_REF]).

The Limits of Mimetic Replication

Mimetics serves as a broader term encompassing the study of all forms of replication. Richard Dawkins' seminal and influential concept of memetics takes this idea further into the domain of semiotic thought. Dawkins claims that since universal Darwinism suggests that replication and natural selection are the primary forces through which the universe comes into being, memes are but a tiny part of a far grander vision. Computer music is increasingly pollinated with ideas from all over the spectrum of the sciences -an art-science [START_REF] Arrell | Pushing the Envelope: Art and Science in the Music of Gérard Grisey[END_REF] in emergence as it is referred to by Gérard Grisey. So how do we dismantle and rebuild our understanding of the musical score into the 'essential' or 'base' form that analyzing animated notation in relation to static notation demands? One that isn't bound by two dimensions X and Y (generally seen as time and pitch in the score space), which would be far too specific for a multimedia focused compositional system to give but one example. As described by John Blacking in his book How Musical is Man, music contains a qualitative dimension. Would a nonsystematic approach to animated notation be better suited to tackling this challenge? Here he describes with exactitude how cultural information is essential to our understanding of music:

'Consider the matter of 'feeling in music,' which is often invoked to distinguish two technically correct performances of the same piece. This doctrine of feeling is in fact based on the recognition of the existence and importance of deep structures in music.' [START_REF] Blacking | How Musical Is Man? (Jessie and John Danz Lectures)[END_REF] Why people seek to represent through abstraction is not a total mystery, yet untangling the twisted ropes of meaning wrapping up every idea anyone has ever conceived probably presents a completely unsurpassable challenge. The utopian desires of universal Darwinism will likely not be realized through ever increasingly complex quantizations of the natural elements, and while defining moieties in an artistic context may be seen as futile by some, the so-called 'memes' that comprise the universal replicators of meaning imagined by Richard Dawkins and significantly expanded upon by Susan Blackmore (even to the point of suggesting that the meme is being superseded by a new unit, the 'teme'), present a very real and useful concept when applied to animated notation analysis.

Defining Mimetic and Memetic Scoring Systems

As mentioned, we propose that closer a musical unit comes to representing a "direct action", the more mimetic it becomes. Within the scope of this definition, the most mimetic score achievable is a person performing any copyable action. Further, this paradigm can be abstracted into the domain of video, and through acousmatic methods, into sound exclusively (such as is the case in many aural musical traditions for example). Lyrebird's and other parrots engage in this practice also, often with a far greater degree of accuracy than many human musicians. Further levels of abstraction can be seen in Ryan Ross Smith's particular brand of animated notation involving radials, cursors and other devices designed to control complex rhythmic coordination in ensemble contexts. Cat Hope's scrolling scores introduce a similar kind of mimesis, as do David Kim-Boyle's AR and 3D scores. Common practice notation introduces a higher degree of assumed knowledge and therefore is heavily dependent on memetic transfer, so in the same sense, direct copying of a gesture resulting in sound is a mimetic transfer, done without requiring a theory of mind, but once the sound begins to stimulate the physiological, auditory system of someone memetic and semiotic processes spring into action.

MIMETIC ORCHESTRATION

With the exception of the first opus (In Memoriam JC Risset 1), whose pitch material was extracted from the analysis of FM synthesis spectra, all the pieces of the cycle presented below constitute mimetic orchestrations of the PRISM laboratory synthesizer, developed by Richard Kronland-Martinet [START_REF] Conan | An intuitive synthesizer of continuous-interaction sounds: Rubbing, scratching, and rolling[END_REF], who worked for thirty years with Jean-Claude Risset at LMA, Marseille, France.

This synthesizer is based on a perceptive model (as opposed to a physical model [START_REF] Ellis | Modalys demonstration[END_REF]) and carries the influence of Risset's exploration of timbre synthesis, examined through the perspective of human perception [START_REF] Risset | Exploration of timbre by analysis and synthesis[END_REF]. The great majority of the electronics in other pieces of the cycle (In Memoriam 2, 3 and 4) makes extensive use of the liquefaction parameter, which turns a continuous sound into small grains evoking the resounding impacts of drops on multiple resonant metallic surfaces, or some form of imaginary rain on metallic chimes. 1 The Bach [START_REF] Agostini | Bach: an environment for computer-aided composition in max[END_REF] library was very helpful for musical transcription, subsequently allowing for transfer to the instrumental domain.

The authors forthcoming doctoral thesis 'Between Mimetics and Memetics' examines the credo assumed by various spectral composers, for whom the very act of composing was equivalent to translation of sounds from the acoustic to the instrumental domain. Classical contemporary music scenes such as those represented in Europe by the Gaudeamus or Darmstadt academies and festivals reveal, however, that such preoccupations are often today very far removed from what young generations of composers seemingly wish to express. Therefore, one can only talk of neo or postspectralism when referring to such techniques. Whilst still taught in institutions like IRCAM, or briefly mentioned as part of the undergraduate composition curricula, one can deplore the fact that this aesthetic canon has seen its day now that technologies (such as the tools presented in the present paper) finally allow more intuitive and user-friendly interfaces to the composer (Bach, Ableton, PRISM synthesizer), auditory and visual computer assistance for microtonal intonation and synchronization adjustments to the performer (SmartVox [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF]), and thus probably more convincing results from an audience's point of view.

Time Domain: Temporal Precision and Mimetic Transfer

At IRCAM in January 2018, Benjamin Matuszewski highly improved the synchronization possibilities of SmartVox by implementing a client-side algorithm that puts back in sync devices whose drift exceeds a certain threshold ( [START_REF] Bell | Audiovisual Scores and Parts Snchronized Over The Web[END_REF], Chapter 4.3). Until this new release, SmartVox had to deal with a more approximate temporality, but it can now explore a wide range of tightly synchronized musical situations, between musicians, electronics and video for instance.

In none-pulsed music, in spite of the great conducting tradition in chamber music and orchestral works, left-to-right scrolling cursors distributed on the performers' devices (as seen in the Decibel ScorePlayer or SmartVox) seem a far more straightforward strategy to obtain tight synchronization rather than the bars and beats 'encoding' (quantification by the composer with or without the help of algorithms) and decoding processes (a compromised interpretation by the instrumentalist, between the rhythmic values written on the page and the gestures of the conductor), inherited from a scoring tradition in which a regular meter was assumed.

The bach.roll object displays notation in proportional time, and outputs notifications of its playback status in real-time. These notifications can be interpreted in Max For Live in order to synchronize 1/ the notation for human players in Bach and 2/ the electronics in Ableton Live. Pieces of the Risset cycle all benefit from this improvement: in the first piece of the cycle, a passage is based on rhythmical games between performers, taking advantage of the cursor-type display of time. 3 In Das Hoheslied, In Memoriam Jean-Claude Risset 3, premiered in June 2019, students of HfMT Hamburg were able to sight-sing (for the very first time) passages which strikingly resembled the target model. 4

Frequency Domain: Harmonic Analysis of Frequency Modulation

Rather than citing the oft-used Shepard-Risset glissando illusion, the author found it more appropriate to re-activate one of the most successful techniques of the beginning of computer music: frequency modulation, which Risset was amongst the first composers to use in his piece Mutations (1969), thanks to Chowning's generous permission. This is why nearly all the harmonic material from In Memoriam J.C. Risset 1 and 3 was generated by FM synthesis.

For frequency analysis, although Iana [START_REF] Todoroff | IANA: A real-time environment for analysis and extraction of frequency components of complex orchestral sounds and its application within a musical realization[END_REF] was formerly used (and also favored by Daniele Ghisi [START_REF] Agostini | Bach: an environment for computer-aided composition in max[END_REF] in some of his transcription patches), the zsa.freqpeak descriptor [START_REF] Malt | Zsa.Descriptors: a library for real-time descriptors analysis[END_REF] offered seemingly more accurate results. A Max For Live device was built for pitch visualization purposes. 5As a reference to Risset's findings regarding the temporal evolution of the harmonic content of digitally recorded trumpet sounds (which becomes richer in high frequency harmonic when loudness increases [START_REF] Risset | Computer study of trumpet tones[END_REF], the evolution of frequency's 'Modulation index' 6 , was orchestrated by successive entries of voices, from the lowest register (bass) to the highest (soprano). 7

Conclusion on Mimetic Spectralism and Vocal Imitation

Some of the tools presented in this chapter show that the possibilities offered by today's technologies would have appealed to the supporters of the 'mimetic spectralism' imagined in the 1970s. If the compositional aesthetics followed by these composers is not to everyone's taste, they may at least provide a fertile ground for artistic/scientific research, because their aims and methods, concerned with the reproducibility of a model, are suitable to measurements and, for instance, quantifiable assessments. 8In a more scientific context, members of the PRISM 9laboratory undertook an experimental study of vocal imitation which recalls the sight-reading experiment in Das Hoheslied, In Memoriam Jean-Claude Risset 3. According to the author, Thomas Bordonné, this study "aimed at determining the main characteristics of sounds used by participants during vocal imitations". Bordonné concludes: "Vocal imitations seem to be a good tool to access perception and determine which aspects of the sounds are relevant" [START_REF] Bordonné | Assessing sound perception through vocal imitations of sounds that evoke movements and materials[END_REF]. In this setup, therefore, the spontaneous vocal response of participants could be interpreted in similar ways to the SmartVox-led reading sessions in which the singers are asked to imitate what they hear.

COMPOSITIONAL/PERFORMATIVE EXPERIMENTS WITH ANIMATED AND DISTRIBUTED NOTATION 4.1 Global Context

Ryan Ross Smith's animatednotation.com website demonstrates that today many composers find fixed common practice notation limiting. To solve this issue, attendees of the Tenor Conference10 have proposed elements of response. With Kagel's Prima Vista (1962/64) setting a major precent, animated notation often relies on a large screen projecting the parts, as most famously exemplified in Smith's compositional practice. The score can therefore be seen by the performers but also by the audience, thus making notation part of the theatrical performance.

Other performance-oriented systems (SmartVox [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF] [12], Zscore [START_REF] Zagorac | Zscore: A distributed system for integrated mixed music composition and performance[END_REF], Decibel [START_REF] Hope | Scoring an animated notation opera -the decibel score player and the role of the digital copyist in 'speechless[END_REF] [19], Maxscore [START_REF] Hajdu | Maxscore: Recent developments[END_REF], comprovisador [START_REF] Louzeiro | Improving sight-reading skills through dynamic notation -the case of comprovisador[END_REF]) endeavor to distribute and synchronize each part of the score on the performer's devices (whether Smartphones, tablets or laptops). With SmartVox for instance, rendering the score in the browser directly revealed itself to be very effective for this kind of setup. Thanks to cross-platform web technologies, the application works with any browser capable device, and no installation is required by the client. The node.js 11 /websocket architecture of SmartVox will hopefully inspire more composers, researchers and developers to investigate the emerging musical practice of distributed notation.

Graphical Notation in Bach

Most pieces performed with SmartVox rely highly on Bach [START_REF] Agostini | Bach: an environment for computer-aided composition in max[END_REF], a realtime computer-aided composition package for Max/MSP. The use of color and shape in pieces like In Memoriam JC Risset 1 or Mit Allen Augen, In Memoriam JC Risset 2 was inspired by Cat Hope [START_REF] Hope | Electronic scores for music: The possibilities of animated notation[END_REF] and Lyndsey Vickery [START_REF] Vickery | Some approaches to representing sound with colour and shape[END_REF], two active composers, researchers, developers of the Decibel ScorePlayer [START_REF] Hope | The decibel scoreplayer -a digital tool for reading graphic notation[END_REF], whose approach to animated graphical notation opens new territories for musical scores today.

Unlike other notation packages in Max (MaxScore [START_REF] Hajdu | Maxscore: Recent developments[END_REF], or the Symbolist [START_REF] Gottfried | Symbolist: An open authoring environment for user-defined symbolic notation[END_REF]) which were imagined as symbolic representations in the first place (Rama Gottfried describes the Symbolist as a version of adobe illustrator in Max), the Bach environment emerged from Open Music [START_REF] Bresson | OpenMusic -Visual Programming Environment for Music Composition, Analysis and Research[END_REF] and computer-aided composition, which explains some of its limitations from a graphical point of view: for instance, it is impossible to insert a picture in a bach.roll (in proportional notation), and the bach.roll object does not support articulations (unlike the bach.score object in bars and beats notation). However, one can get around this graphical limitation by adjusting the duration line settings (see Figure 2). The use of colors is also easily customizable with the help of 'slots'.

In spite of its few display limitations, one of the strengths of Bach consists of its ability to control synthesizers from the notation directly. Slots can therefore be understood as metadata or temporal automations that can subsequently be mapped onto any Max-programmed synthesizers, enabling staves of a score to be manipulated as tracks of a DAW12 .

Distributed Musical Notation

Composers and researchers increasingly acknowledge the strong analogy which can be drawn between the traditional 'score and parts' musical practice led by a conductor, and the modern distributed systems or web applications (Zscore [START_REF] Zagorac | Zscore: A distributed system for integrated mixed music composition and performance[END_REF] -MASD [START_REF] Nathan | Musician assistance and score distribution (masd)[END_REF] -SmartVox [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF]), in which multiple clients coordinate their actions by passing messages to one another.

The Tenor 2018 conference in Montreal revealed an interesting similarity between the Decibel ScorePlayer and SmartVox, in the sense that the two software packages are rather elementary solutions both converging towards the score player performance-oriented paradigm, whilst other notation packages (Bach, Maxscore, Symbolist...) were also designed for more elaborate computer-aided composition and real-time processes. Although the Decibel ScorePlayer is today's most reliable iOS application solution for distributed animated notation, Cat Hope and Aaron Wyatt have evoked the possibility to migrate their system to the browser, for instant access over the internet presumably, but also optimization of networking issues, and cheaper production cost in local settings-e.g. for projects involving over fifty devices, the iPad becomes a very expensive solution). The most likely architecture to allow this transfer of technology would be a node.js server 13 (server-side javascript), with the WebSocket communication protocol, a solution used by SmartVox as early as 2015, thanks to Norbert Schnell and Benjamin Matuszewski from IRCAM in Paris. SmartVox sends and synchronises mp4 audiovisual scores, which has demonstrated undeniable robustness in large scale concerts and rehearsals, but also reveals the potential weakness of a 'non-realtime' solution (as a sort of fixed multichannel tape) in which performances of the piece would be similar each time. Other composers/researchers (Georg Hajdu, Rama Gottfried, Slavko Zagorac) are currently investigating forward thinking solutions which will allow the control of SVG (Scalable Vector Graphic) directly on the clientside HTML page. The authors MaxScore.Netcanvas object acted as a precursor to a later project which made use of this notion, through performance of the 50 part real-time generated piece Magnetic Visions 50 relying on WebSockets to transfer instantaneously generated score fragments. The architecture chosen for this by Georg Hajdu and Rama Gottfried is node.js, sending osc over WebSockets. This project resulted in a realtime distributed 144-part site-specific composition in Hamburg in May 2019, which was justifiably well received due in part to its technically ambitious and groundbreaking nature.

Augmented Reality Distributed Notation

In Memoriam JC Risset 114 , premiered in September 2018 at the Gaudeamus Festival (Utrecht), and subsequently performerd in New York in ICMC-NYCEMF 2019, constitutes the author's first experiment using head-mounted displays for notational purposes, principally inspired by Benedict Carey's SpectraScore VR [START_REF] Carey | Spectrascore vr: Networkable virtual reality software tools for real-time composition and performance[END_REF] in this regards. By simply displaying each part of the score over the heads of the performers (for flute and clarinet only), the piece opened promssing perspectives.

Just as traditional scores placed on a music stand, screenscores displayed on a tablet (for instrumentalists) or on a phone (for singers) oblige musicians to look and orientate their body constantly in the direction of the score. This well-established convention of the classical concert setup considerably limits the possibilities of staging music, in a theatrical context for instance. In such cases as the Ictus Ensemble's interpretation of Vortex Temporum by Gérard Grisey 15 , where the musicians had to learn the score by heart, and perform without a conductor, Wi-Fisynchronized head-mounted displays might be an interesting way to help musicians coordinate in time and space, while moving on stage or around the audience, without insurmountable performance challenges. The idea was therefore explored further on a larger scale in Mit Allen Augen, In Memoriam JC Risset 2. 16According to the performers' feedback, head-mounted setups provide a large and comfortable display, since the environment is still visible around the score (see Figure 3), or through the score in the case of holographic display (such as the Aryzon headset for instance). The performers also showed interest in their ability to move freely on stage or elsewhere (the piece was choreographed differently according to the venue: in a church, the flute and clarinet started the piece behind the audience and gradually approached the altar), which relates to the term phygital (physical+digital) coined by Fabrizio Lamberti [START_REF] Lupetti | Phygital play hri in a new gaming scenario[END_REF], who claims that with AR and VR, the possibilities of physicalization of gaming will soon encompass other fields. While awaiting more discrete (such as Google glasses or Vufine displays, which would be invisible from an au-dience's point of view) but still affordable solution, AR opens vast domains for further research, which could go far beyond the mere display of animated notation. However, important questions then arise regarding what would be pertinent to achieve with such technology: in a VR context for instance, with a player on stage, how can the limitation due to the destabilization of the performer's proprioception be overcome? Also, now that any form of immersive score can be prototyped, 17 how would this be of musical interest, and how could this have a convincing musical impact on the compositional/performative outcome? SmartVox, for instance, delivers and synchronizes mp4 files, and should soon support 360-degree videos 18 , but how can this benefit the performer in a musical sense? Australia holds today one of the world's largest contingents of composers/researchers working in animated and XR notation, and Australian composers such as David Kim Boyle [START_REF] Kim-Boyle | The 3-d score[END_REF] and the author [START_REF] Carey | Spectrascore vr: Networkable virtual reality software tools for real-time composition and performance[END_REF], who specifically investigate 3D-scores in VR environments, present elements of response to this issue.

NETWORKED MUSICAL PERFORMANCES -NMPS

5.1 SmartVox.eu, Score Distribution over the Web and Remote NMPs

With the exponential growth of the web, hosting Smartvox 19 on the internet (i.e. on a remote server rather than a local one) appeared as a necessity. However we demonstrated (in Chapter 4.2 'Measurements of timing accuracy' [START_REF] Bell | Audiovisual Scores and Parts Snchronized Over The Web[END_REF]) that, although the synchronization of different parts was quite accurate in this way, local solutions remained safer (in the same room, over Wi-Fi). Also, notwithstanding the fact that SmartVox undoubtedly belongs to the realm of Networked Music Performances, it became clear that its practical application falls under the 'local NPMs' sub-category defined by Gabrielli and Squartini [START_REF] Gabrielli | Wireless Networked Music Performance[END_REF].

Since the advent of the internet, thorough research has been undertaken in the realm of remote Networked Musical Performances (NMP) [START_REF] Rottondi | An overview on networked music performance technologies[END_REF]. Today however, local NMPs still seem today more viable, both technically and artistically speaking. Despite many 'millennials' being known for their enthusiastic engagement in online gaming (i.e. remotely), with friend avatars or anonymous players often distributed widely around the globe, many examples would show that musicians still feel more inclined to reading a score or improvising together in the same room. In Embodiment and Disembodiment in Networked Music Performance [START_REF] Hajdu | Embodiment and disembodiment in networked music performance[END_REF] Georg Hajdu explains that "appreciation [of the musical experience] relies on the plausibility between physical action and sonic result." Since the emergence of NMPs, 20 some disappointment arose from the fact that, from the audience's 17 Such as the ones imagined by Mauricio Kagel's film Ludwig Van (1969), see for instance: https://youtu.be/7l8vPWFIgxI?t=1591 18 This could be done by simply implementing a 360 mediaplayer in HTML5, e.g.: https://bitmovin.com/demos/vr-360 19 Each instrumental/vocal part of the piece And the Sea is accessible through the following url www.SmartVox.eu, and can be accessed simultaneously from e.g., an iPad for the flute, Android tablets for piano and cello, and a phone for the singer. A trailer of the premiere of the piece is accessible here: https://youtu.be/prcXUbhd-ZY 20 The American computer music network band 'the Hub', formed in 1986, contributed to the popularization of this new genre. point of view (but also for the musicians themselves), very little can be seen and therefore understood, which worsens with distant performers: "Because of the remoteness of the participants locations, these actions may not always be perceived directly or immediately [...], classical cause-andeffect relationships [...] are replaced by plausibility, that is the amount to which performers and spectators are capable of 'buying' the outcome of a performance by building mental maps of the interaction. In NMP, this can be facilitated by the use of avatars, projected visually, and carefully orchestrated dramaturgies, involving participants in gamelike scenarios." Many VR environments today focus on this interaction between a physical action and its sonic result. New Atlantis ( [START_REF] Sinclair | New Atlantis: Audio Experimentation in a Shared Online World[END_REF]), for instance, is a multi-user sound exploration platform in which several players can interact with each other. 21 With their ability to represent avatars of musical performers, these new interfaces may soon have the ability to recreate the visual entity producing sound (or music). By recreating virtual causal links between an action and its sonic result, these online game interfaces should provide users with the missing visual element that prevent NPMs from becoming a genuine globalized musical practice.

The 'BabelBox', a Raspberry Pi Hardware Embedded System Solution for Local NMPs

SmartVox and MaxScore.Netcanvas have proved to be suitable for large scale projects such as le temps des nuages 22 and Magnetic Visions 50, in which eighty singers and musicians [START_REF] Bell | Audiovisual Scores and Parts Snchronized Over The Web[END_REF] and fifty musicians had their score synchronized through the same network respectively. These productions still enjoy increasing interest from choirs and ensembles, 23 requiring a very modest technical setup (only one Wi-Fi access point, e.g. Ubiquiti Unifi) for choirs up to thirty singers, with a node.js server running on a Mac computer. However, in the more intimate context of chamber music (as in In Memoriam JC Risset 1), the focus is slightly different: the network load is much lighter, which encouraged finding a minimal hardware solution, in order to make possible rehearsals without the physical presence of the composer or the mobilization of a technician only to setup a network. Installing the server on the performer's computer remotely has often been successful with musicians unfamiliar with technology, thanks to the flexibility of the Node Package Manager (NPM), which reduces the installation of SmartVox to a few command lines. 24 This installation process nevertheless remained an obstacle for the dissemination of SmartVox. In search of a light plugand-play dedicated system to be sent over the post, the Raspberry Pi quickly appeared as the best option to host SmartVox on an embedded system. Node.js runs on Rasp- 21 Towards the end of the following extract, three players can be observed producing sounds together: https://vimeo.com/264626943 22 A recording of the piece is available at the following address: https://youtu.be/SyFdR2HiF00 23 SmartVox was used for the rehearsals and performance of To See The Invisible, an opera by Emily Howard, Aldeburgh, Snape Maltings 2018https://snapemaltings.co.uk/concerts-history/aldeburgh-festival-2018/to-see-the-invisible/ 24 SmartVox is open source and ready to download via GitHub: https://github.com/belljonathan50/SmartVox0.1.

bian, and SmartVox proved to be very stable on a Raspberry Pi 3, so, once installed, the only two steps for a 0-conf deliverable hardware were:

• Setting up a static address from the dedicated router (e.g. tp-link...). • Starting SmartVox at boot.

Starting a script at boot can be done on Raspbian with a file containing the following in the etc/systemd/system: This low-cost system (less than 65 C, for a Raspberry Pi and a router) now allows the sending of ready-to-use scores.

Once the system is power-supplied, all the performers need to do is to join the dedicated Wi-Fi, and type the static IP address of the server on their smartphone/tablet (i.e. for the performers: 192.168.0.100:8000, and for the conductor: 192.168.0.100:8000/conductor). In January 2019, the system was rented to the Caen French conservatoire via Ba-belScores 25 , thus proposing a rental of performing scores (separate parts) of a new kind.

CONCLUSION

Animated notation, score distribution, AR and VR technologies were here presented as tools for composition and performances in which mimesis is examined under multiple notational perspectives. The mimetic value of notation relates, on the 'prescriptive' side, to its ability to mimic an instrumental gesture (such as the representation of the position of fingers on tablature notation), but also, on the 'descriptive' side, to its ability to help performers imitate a target sound, as exemplified in the workflow of spectral composers 26 . Initially conceived almost exclusively as a rehearsal tool for choral practices [START_REF] Bell | SmartVox. A web-based distributed media player as notation tool for choral practices[END_REF] [START_REF] Bell | Audiovisual Scores and Parts Snchronized Over The Web[END_REF], recent use cases have shown that SmartVox is better described as a distributed score player, allowing for vocalists, instruments and electronics or multimedia to interact in a Networked Music Performance.

  Figure 1 shows how Ableton's playback controls can be accessed through the live-set path of the live object model (LOM), which makes constant back and forth playbacks possible between the score and the electronics, during the compositional process. This interface facilitated the composition of Mit Allen Augen, In Memoriam J.-C. Risset 2, a piece involving large forces performed in Paris in March 2019 (12 voices, 12 instruments and electronics).

2

 2

Figure 1 .

 1 Figure 1. Max For Live device syncing Bach and Ableton.

Figure 2 .

 2 Figure 2. Duration line adjustment in Bach.

Figure 3 .

 3 Figure 3. Score display from the performer's point of view.

[

  U n i t ] D e s c r i p t i o n =My s e r v i c e [ S e r v i c e ] E x e c S t a r t = / home / p i / D e s k t o p / h e l l o . s h [ I n s t a l l ] WantedBy= m u l t i-u s e r . t a r g e t With the hello.sh script containing the following to launch the server: # ! / b i n / b a s h cd / home / p i / D e s k t o p / r i s s e t npm r u n s t a r t e x e c b a s h

Figure 4 .

 4 Figure 4. Score display from the performer's of view.

A liquefation demonstration is available here: https://youtu.be/2kdIaqAhUGs

The following example shows the convenience of the Bach/Ableton inter-application communication https://youtu.be/VJvY5wYl cM

A rhythmical passage in In Memoriam Jean-Claude Risset 1 https://youtu.be/hQtyu1dcCaI?t=349

A Target sound is followed by its imitation by the choir in a sightreading session of Das Hoheslied, In Memoriam Jean-Claude Risset 3 https://youtu.be/EHYq9nFF6sE

Real-time spectral analysis with Bach and Zsa.FreqPeak https://youtu.be/D6mCgx4pSxs

See https://youtu.be/OnT-Zgkh5MA for demo purposes.

See https://youtu.be/sgSjIpSD8yQ.

As, for instance, in the aforementioned Hambourg's choir sightreading example: Das Hoheslied, In Memoriam Jean-ClaudeRisset 3.

[START_REF] Ellis | Modalys demonstration[END_REF] https://www.prism.cnrs.fr/

http://www.tenor-conference.org/

Server-side JavaScript, see: https://nodejs.org/en/

see https://youtu.be/s4qS2khwkT0 for demonstration.

According to a private email conversation with the developper Aaron Wyatt.

A recording of the piece is available at the following address: https://youtu.be/hQtyu1dcCaI

See: https://youtu.be/JFvrYy6EeWE

A recording of the piece is available at the following address: https://youtu.be/ET O BgF W x04

Babelscores (https://www.babelscores.com/) is an online score database for classical contemporary music, currently actively supporting the SmartVox project: http://1uh2.mj.am/nl2/1uh2/lgi4u.html.

Composers for who the rhythmic and harmonic characteristics of a recorded or synthesised sound serve a as basis for composition and orchestration.

Acknowledgments

We would like to thank Cat Hope, Lyndsey Vickery, Georg Hajdu, Daniele Ghisi, Benjamin Matuszewski, Norbert Schnell and Richard Kronland-Martinet.