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Claudio Monteverdi

Claudio Giovanni Antonio Monteverdi (baptized 15 May 1567 – 29 November 1643) was an Italian composer, choirmaster and string player. A composer of both secular and sacred music, and a pioneer in the development of opera, he is considered a crucial transitional figure between the Renaissance and Baroque periods of music history.

Born in Cremona, where he undertook his first musical studies and compositions, Monteverdi developed his career first at the court of Mantua (c. 1590–1613) and then until his death in the Republic of Venice where he was maestro di cappella at the basilica of San Marco. His surviving letters give insight into the life of a professional musician in Italy of the period, including problems of income, patronage and politics.

Much of Monteverdi's output, including many stage works, has been lost. His surviving music includes nine books of madrigals, large-scale religious works, such as his Vespro della Beata Vergine (Vespers for the Blessed Virgin) of 1610, and three complete operas. His opera L'Orfeo (1607) is the earliest of the genre still widely performed; towards the end of his life he wrote works for Venice, including Il ritorno d'Ulisse in patria and L'incoronazione di Poppea.

While he worked extensively in the tradition of earlier Renaissance polyphony, as evidenced in his madrigals, he undertook great developments in form and melody, and began to employ the basso continuo technique, distinctive of the Baroque. No stranger to controversy, he defended his sometimes novel techniques as elements of a seconda pratica, contrasting with the more orthodox earlier style which he termed the prima pratica. Largely forgotten during the eighteenth and much of the nineteenth centuries, his works enjoyed a rediscovery around the beginning of the twentieth century. He is now established both as a significant influence in European musical history and as a composer whose works are regularly performed and recorded.

Cremona: 1567–1591
Monteverdi was baptised in the church of SS Nazaro e Celso, Cremona, on 15 May 1567. The register records his name as "Claudio Zuan Antonio" the son of "Messer Baldasar Mondeverdo". He was the first child of the apothecary Baldassare Monteverdi and his first wife Maddalena (née Zignani); they had married early the previous year. Claudio's brother Giulio Cesare Monteverdi (b. 1573) was also to become a musician; there were two other brothers and two sisters from Baldassare's marriage to Maddalena and his subsequent marriage in 1576 or 1577. Cremona was close to the border of the Republic of Venice, and not far from the lands controlled by the Duchy of Mantua, in both of which states Monteverdi was later to establish his career.

There is no clear record of Monteverdi's early musical training, or evidence that (as is sometimes claimed) he was a member of the Cathedral choir or studied at Cremona University. Monteverdi's first published work, a set of motets, Sacrae cantiunculae (Sacred Songs) for three voices, was issued in Venice in 1582, when he was only fifteen years old. In this, and his other initial publications, he describes himself as the pupil of Marc'Antonio Ingegneri, who was from 1581 (and possibly from 1576) to 1592 the maestro di cappella at Cremona Cathedral. The musicologist Tim Carter deduces that Ingegneri "gave him a solid grounding in counterpoint and composition", and that Monteverdi would also have studied playing instruments of the viol family and singing.

Monteverdi's first publications also give evidence of his connections beyond Cremona, even in his early years. His second published work, Madrigali spirituali (Spiritual Madrigals, 1583), was printed at Brescia. His next works (his first published secular compositions) were sets of five-part madrigals, according to his biographer Paolo Fabbri: "the inevitable proving ground for any composer of the second half of the sixteenth century ... the secular genre par excellence". The first book of madrigals (Venice, 1587) was dedicated to Count Marco Verità of Verona; the second book of madrigals (Venice, 1590) was dedicated to the President of the Senate of Milan, Giacomo Ricardi, for whom he had played the viola da braccio in 1587.

Court musician

In the dedication of his second book of madrigals, Monteverdi had described himself as a player of the vivuola (which could mean either viola da gamba or viola da braccio). In 1590 or 1591 he entered the service of Duke Vincenzo I Gonzaga of Mantua; he recalled in his dedication to the Duke of his third book of madrigals (Venice, 1592) that "the most noble exercise of the vivuola opened to me the fortunate way into your service." In the same dedication he compares his instrumental playing to "flowers" and his compositions as "fruit" which as it matures "can more worthily and more perfectly serve you", indicating his intentions to establish himself as a composer.

Duke Vincenzo was keen to establish his court as a musical centre, and sought to recruit leading musicians. When Monteverdi arrived in Mantua, the maestro di capella at the court was the Flemish musician Giaches de Wert. Other notable musicians at the court during this period included the composer and violinist Salomone Rossi, Rossi's sister, the singer Madama Europa, and Francesco Rasi. Monteverdi married the court singer Claudia de Cattaneis in 1599; they were to have three children, two sons (Francesco, b. 1601 and Massimiliano, b. 1604), and a daughter who died soon after birth in 1603. Monteverdi's brother Giulio Cesare joined the court musicians in 1602.

When Wert died in 1596, his post was given to Benedetto Pallavicino, but Monteverdi was clearly highly regarded by Vincenzo and accompanied him on his military campaigns in Hungary (1595) and also on a visit to Flanders in 1599. Here at the town of Spa he is reported by his brother Giulio Cesare as encountering, and bringing back to Italy, the canto alla francese. (The meaning of this, literally "song in the French style", is debatable, but may refer to the French-influenced poetry of Gabriello Chiabrera, some of which was set by Monteverdi in his Scherzi musicali, and which departs from the traditional Italian style of lines of 9 or 11 syllables). Monteverdi may possibly have been a member of Vincenzo's entourage at Florence in 1600 for the marriage of Maria de' Medici and Henry IV of France, at which celebrations Jacopo Peri's opera Euridice (the earliest surviving opera) was premiered. On the death of Pallavicino in 1601, Monteverdi was confirmed as the new maestro di capella.

Artusi controversy and seconda pratica

At the turn of the 17th century, Monteverdi found himself the target of musical controversy. The influential Bolognese theorist Giovanni Maria Artusi attacked Monteverdi's music (without naming the composer) in his work L'Artusi, overo Delle imperfettioni della moderna musica (Artusi, or On the imperfections of modern music) of 1600, followed by a sequel in 1603. Artusi cited extracts from Monteverdi's works not yet published (they later formed parts of his fourth and fifth books of madrigals of 1603 and 1605), condemning their use of harmony and their innovations in use of musical modes, compared to orthodox polyphonic practice of the sixteenth century. Artusi attempted to correspond with Monteverdi on these issues; the composer refused to respond, but found a champion in a pseudonymous supporter, "L'Ottuso Academico" ("The Obtuse Academic"). Eventually Monteverdi replied in the preface to the fifth book of madrigals that his duties at court prevented him from a detailed reply; but in a note to "the studious reader", he claimed that he would shortly publish a response, Seconda Pratica, overo Perfettione della Moderna Musica (The Second Style, or Perfection of Modern Music). This work never appeared, but a later publication by Claudio's brother Giulio Cesare made it clear that the seconda pratica which Monteverdi defended was not seen by him as a radical change or his own invention, but was an evolution from previous styles (prima pratica) which was complementary to them.

This debate seems in any case to have raised the composer's profile, leading to reprints of his earlier books of madrigals. Some of his madrigals were published in Copenhagen in 1605 and 1606, and the poet Tommaso Stigliani (1573–1651) published a eulogy of him in his 1605 poem "O sirene de' fiumi". The composer of madrigal comedies and theorist Adriano Banchieri wrote in 1609: "I must not neglect to mention the most noble of composers, Monteverdi ... his expressive qualities are truly deserving of the highest commendation, and we find in them countless examples of matchless declamation ... enhanced by comparable harmonies." The modern music historian Massimo Ossi has placed the Artusi issue in the context of Monteverdi's artistic development: "If the controversy seems to define Monteverdi's historical position, it also seems to have been about stylistic developments that by 1600 Monteverdi had already outgrown".

The non-appearance of Monteverdi's promised explanatory treatise may have been a deliberate ploy, since by 1608, by Monteverdi's reckoning, Artusi had become fully reconciled to modern trends in music, and the seconda pratica was by then well established; Monteverdi had no need to revisit the issue. On the other hand, letters to Giovanni Battista Doni of 1632 show that Monteverdi was still preparing a defence of the seconda practica, in a treatise entitled Melodia; he may still have been working on this at the time of his death ten years later.

Opera, conflict and departure
In 1606 Vincenzo's heir Francesco commissioned from Monteverdi the opera L'Orfeo, to a libretto by Alessandro Striggio, for the Carnival season of 1607. It was given two performances in February and March 1607; the singers included, in the title role, Rasi, who had sung in the first performance of Euridice witnessed by Vincenzo in 1600. This was followed in 1608 by the opera L'Arianna (libretto by Ottavio Rinuccini), intended for the celebration of the marriage of Francesco to Margherita of Savoy. All the music for this opera is lost apart from Ariadne's Lament, which became extremely popular. To this period also belongs the ballet entertainment Il ballo delle ingrate.

The strain of the hard work Monteverdi had been putting into these and other compositions was exacerbated by personal tragedies. His wife died in September 1607 and the young singer Caterina Martinelli, intended for the title role of Arianna, died of smallpox in March 1608. Monteverdi also resented his increasingly poor financial treatment by the Gonzagas. He retired to Cremona in 1608 to convalesce, and wrote a bitter letter to Vincenzo's minister Annibale Chieppio in November of that year seeking (unsuccessfully) "an honourable dismissal". Although the Duke increased Monteverdi's salary and pension, and Monteverdi returned to continue his work at the court, he began to seek patronage elsewhere. After publishing his Vespers in 1610, which were dedicated to Pope Paul V, he visited Rome, ostensibly hoping to place his son Francesco at a seminary, but apparently also seeking alternative employment. In the same year he may also have visited Venice, where a large collection of his church music was being printed, with a similar intention.

Duke Vincenzo died on 18 February 1612. When Francesco succeeded him, court intrigues and cost-cutting led to the dismissal of Monteverdi and his brother Giulio Cesare, who both returned, almost penniless, to Cremona. Despite Francesco's own death from smallpox in December 1612, Monteverdi was unable to return to favour with his successor, his brother Cardinal Ferdinando Gonzaga. In 1613, following the death of Giulio Cesare Martinengo, Monteverdi auditioned for his post as maestro at the basilica of San Marco in Venice, for which he submitted music for a Mass. He was appointed in August 1613, and given 50 ducats for his expenses (of which he was robbed, together with his other belongings, by highwaymen at Sanguinetto on his return to Cremona).

Maturity: 1613–1630

Martinengo had been ill for some time before his death and had left the music of San Marco in a fragile state. The choir had been neglected and the administration overlooked. When Monteverdi arrived to take up his post, his principal responsibility was to recruit, train, discipline and manage the musicians of San Marco (the capella), who amounted to about 30 singers and six instrumentalists; the numbers could be increased for major events. Among the recruits to the choir was Francesco Cavalli, who joined in 1616 at the age of 14; he remained connected with San Marco throughout his life, and developed a close association with Monteverdi. Monteverdi also sought to expand the repertory, including not only the traditional a cappella repertoire of Roman and Flemish composers, but also examples of the modern style which he favoured, including the use of continuo and other instruments. Apart from this he was of course expected to compose music for all the major feasts of the church. This included a new mass each year for Holy Cross Day and Christmas Eve, cantatas in honour of the Venetian Doge, and numerous other works (many of which are lost). Monteverdi was also free to obtain income by providing music for other Venetian churches and for other patrons, and was frequently commissioned to provide music for state banquets. The Procurators of San Marco, to whom Monteverdi was directly responsible, showed their satisfaction with his work in 1616 by raising his annual salary from 300 ducats to 400.

The relative freedom which the Republic of Venice afforded him, compared to the problems of court politics in Mantua, are reflected in Monteverdi's letters to Striggio, particularly his letter of 13 March 1620, when he rejects an invitation to return to Mantua, extolling his present position and finances in Venice, and referring to the pension which Mantua still owes him. Nonetheless, remaining a Mantuan citizen, he accepted commissions from the new Duke Ferdinando, who had formally renounced his position as Cardinal in 1616 to take on the duties of state. These included the balli Tirsi e Clori (1616) and Apollo (1620), an opera Andromeda (1620) and an intermedio, Le nozze di Tetide, for the marriage of Ferdinando with Caterina de' Medici (1617). Most of these compositions were extensively delayed in creation – partly, as shown by surviving correspondence, through the composer's unwillingness to prioritise them, and partly because of constant changes in the court's requirements. They are now lost, apart from Tirsi e Clori, which was included in the seventh book of madrigals (published 1619) and dedicated to the Duchess Caterina, for which the composer received a pearl necklace from the Duchess. A subsequent major commission, the opera La finta pazza Licori, to a libretto by Giulio Strozzi, was completed for Fernando's successor Vincenzo II, who succeeded to the dukedom in 1626. Because of the latter's illness (he died in 1627), it was never performed, and it is now also lost.

Monteverdi also received commissions from other Italian states and from their communities in Venice. These included, for the Milanese community in 1620, music for the Feast of St. Charles Borromeo, and for the Florentine community a Requiem Mass for Cosimo II de' Medici (1621). Monteverdi acted on behalf of Paolo Giordano II, Duke of Bracciano, to arrange publication of works by the Cremona musician Francesco Petratti. Among Monteverdi's private Venetian patrons was the nobleman Girolamo Mocenigo, at whose home was premiered in 1624 the dramatic entertainment Il combattimento di Tancredi e Clorinda based on an episode from Torquato Tasso's La Gerusalemme liberata. In 1627 Monteverdi received a major commission from Odoardo Farnese, Duke of Parma, for a series of works, and gained leave from the Procurators to spend time there during 1627 and 1628.

Monteverdi's musical direction received the attention of foreign visitors. The Dutch diplomat and musician Constantijn Huygens, attending a Vespers service at the church of SS. Giovanni e Lucia, wrote that he "heard the most perfect music I had ever heard in my life. It was directed by the most famous Claudio Monteverdi ... who was also the composer and was accompanied by four theorbos, two cornettos, two bassoons, one basso de viola of huge size, organs and other instruments ...". Monteverdi wrote a mass, and provided other musical entertainment, for the visit to Venice in 1625 of the Crown Prince Władysław of Poland, who may have sought to revive attempts made a few years previously to lure Monteverdi to Warsaw. He also provided chamber music for Wolfgang Wilhelm, Count Palatine of Neuburg, when the latter was paying an incognito visit to Venice in July 1625.

Correspondence of Monteverdi in 1625 and 1626 with the Mantuan courtier Ercole Marigliani reveals an interest in alchemy, which apparently Monteverdi had taken up as a hobby. He discusses experiments to transform lead into gold, the problems of obtaining mercury, and mentions commissioning special vessels for his experiments from the glassworks at Murano.

Despite his generally satisfactory situation in Venice, Monteverdi experienced personal problems from time to time. He was on one occasion – probably because of his wide network of contacts – the subject of an anonymous denunciation to the Venetian authorities alleging that he supported the Habsburgs. He was also subject to anxieties about his children. His son Francesco, while a student of law at Padua in 1619, was spending in Monteverdi's opinion too much time with music, and he, therefore, moved him to the University of Bologna. This change did not have the desired result, and it seems that Monteverdi resigned himself to Francesco having a musical career – he joined the choir of San Marco in 1623. His other son Massimiliano, who graduated in medicine, was arrested by the Inquisition in Mantua in 1627 for reading forbidden literature. Monteverdi was obliged to sell the necklace he had received from Duchess Caterina to pay for his son's (eventually successful) defence. Monteverdi wrote at the time to Striggio seeking his help, and fearing that Massimiliano might be subject to torture; it seems that Striggio's intervention was helpful. Money worries at this time also led Monteverdi to visit Cremona to secure for himself a church canonry.

Pause and priesthood: 1630–1637
A series of disturbing events troubled Monteverdi's world in the period around 1630. Mantua was invaded by Habsburg armies in 1630, who besieged the plague-stricken town, and after its fall in July looted its treasures, and dispersed the artistic community. The plague was carried to Mantua's ally Venice by an embassy led by Monteverdi's confidante Striggio, and over a period of 16 months led to over 45,000 deaths, leaving Venice's population in 1633 at just above 100,000, the lowest level for about 150 years. Among the plague victims was Monteverdi's assistant at San Marco, and a notable composer in his own right, Alessandro Grandi. The plague and the after-effects of war had an inevitable deleterious effect on the economy and artistic life of Venice. Monteverdi's younger brother Giulio Cesare also died at this time, probably from the plague.

By this time Monteverdi was in his sixties, and his rate of composition seems to have slowed down. He had written a setting of Strozzi's Proserpina rapita (The Abduction of Proserpina), now lost except for one vocal trio, for a Mocenigo wedding in 1630, and produced a Mass for deliverance from the plague for San Marco which was performed in November 1631. His set of Scherzi musicali was published in Venice in 1632. In 1631, Monteverdi was admitted to the tonsure, and was ordained deacon, and later priest, in 1632. Although these ceremonies took place in Venice, he was nominated as a member of Diocese of Cremona; this may imply that he intended to retire there.

Late flowering: 1637–1643

The opening of the opera house of San Cassiano in 1637, the first public opera house in Europe, stimulated the city's musical life and coincided with a new burst of the composer's activity. The year 1638 saw the publication of Monteverdi's eighth book of madrigals and a revision of the Ballo delle ingrate. The eighth book contains a ballo, "Volgendi il ciel", which may have been composed for the Holy Roman Emperor, Ferdinand III, to whom the book is dedicated. The years 1640–1641 saw the publication of the extensive collection of church music, Selva morale e spirituale. Among other commissions, Monteverdi wrote music in 1637 and 1638 for Strozzi's "Accademia degli Unisoni" in Venice, and in 1641 a ballet, La vittoria d'Amore, for the court of Piacenza.

Monteverdi was still not entirely free from his responsibilities for the musicians at San Marco. He wrote to complain about one of his singers to the Procurators, on 9 June 1637: "I, Claudio Monteverdi ... come humbly ... to set forth to you how Domenicato Aldegati ... a bass, yesterday morning ... at the time of the greatest concourse of people ... spoke these exact words ...'The Director of Music comes from a brood of cut-throat bastards, a thieving, fucking, he-goat ... and I shit on him and whoever protects him ....

Monteverdi's contribution to opera at this period is notable. He revised his earlier opera L'Arianna in 1640 and wrote three new works for the commercial stage, Il ritorno d'Ulisse in patria (The Return of Ulysses to his Homeland, 1640, first performed in Bologna with Venetian singers), Le nozze d'Enea e Lavinia (The Marriage of Aeneas and Lavinia, 1641, music now lost), and L'incoronazione di Poppea (The Coronation of Poppea, 1643). The introduction to the printed scenario of Le nozze d'Enea, by an unknown author, acknowledges that Monteverdi is to be credited for the rebirth of theatrical music and that "he will be sighed for in later ages, for his compositions will surely outlive the ravages of time."

In his last surviving letter (20 August 1643), Monteverdi, already ill, was still hoping for the settlement of the long-disputed pension from Mantua, and asked the Doge of Venice to intervene on his behalf. He died in Venice on 29 November 1643, after paying a brief visit to Cremona, and is buried in the Church of the Frari. He was survived by his sons; Masimilliano died in 1661, Francesco after 1677.

Background: Renaissance to Baroque
There is a consensus among music historians that a period extending from the mid-15th century to around 1625, characterised in Lewis Lockwood's phrase by "substantial unity of outlook and language", should be identified as the period of "Renaissance music". Musical literature has also defined the succeeding period (covering music from approximately 1580 to 1750) as the era of "Baroque music". It is in the late-16th to early-17th-century overlap of these periods that much of Monteverdi's creativity flourished; he stands as a transitional figure between the Renaissance and the Baroque.

In the Renaissance era, music had developed as a formal discipline, a "pure science of relationships" in the words of Lockwood. In the Baroque era it became a form of aesthetic expression, increasingly used to adorn religious, social and festive celebrations in which, in accordance with Plato's ideal, the music was subordinated to the text. Solo singing with instrumental accompaniment, or monody, acquired greater significance towards the end of the 16th century, replacing polyphony as the principal means of dramatic music expression. This was the changing world in which Monteverdi was active. Percy Scholes in his Oxford Companion to Music describes the "new music" thus: "[Composers] discarded the choral polyphony of the madrigal style as barbaric, and set dialogue or soliloquy for single voices, imitating more or less the inflexions of speech and accompanying the voice by playing mere supporting chords. Short choruses were interspersed, but they too were homophonic rather than polyphonic."

Novice years: Madrigal books 1 and 2

Marc'Antonio Ingegneri, Monteverdi's first tutor, was a master of the musica reservata vocal style, which involved the use of chromatic progressions and word-painting; Monteverdi's early compositions were grounded in this style. Ingegneri was a traditional Renaissance composer, "something of an anachronism", according to Arnold, but Monteverdi also studied the work of more "modern" composers such as Luca Marenzio, Luzzasco Luzzaschi, and a little later, Giaches de Wert, from whom he would learn the art of expressing passion. He was a precocious and productive student, as indicated by his youthful publications of 1582–83. Mark Ringer writes that "these teenaged efforts reveal palpable ambition matched with a convincing mastery of contemporary style", but at this stage they display their creator's competence rather than any striking originality. Geoffrey Chew classifies them as "not in the most modern vein for the period", acceptable but out-of-date. Chew rates the Canzonette collection of 1584 much more highly than the earlier juvenilia: "These brief three-voice pieces draw on the airy, modern style of the villanellas of Marenzio, [drawing on] a substantial vocabulary of text-related madrigalisms".

The canzonetta form was much used by composers of the day as a technical exercise, and is a prominent element in Monteverdi's first book of madrigals published in 1587. In this book, the playful, pastoral settings again reflect the style of Marenzio, while Luzzaschi's influence is evident in Monteverdi's use of dissonance. The second book (1590) begins with a setting modelled on Marenzio of a modern verse, Torquato Tasso's "Non si levav' ancor", and concludes with a text from 50 years earlier: Pietro Bembo's "Cantai un tempo". Monteverdi set the latter to music in an archaic style reminiscent of the long-dead Cipriano de Rore. Between them is "Ecco mormorar l'onde", strongly influenced by de Wert and hailed by Chew as the great masterpiece of the second book.

A thread common throughout these early works is Monteverdi's use of the technique of imitatio, a general practice among composers of the period whereby material from earlier or contemporary composers was used as models for their own work. Monteverdi continued to use this procedure well beyond his apprentice years, a factor that in some critics' eyes has compromised his reputation for originality.

Madrigals 1590–1605: books 3, 4, 5
Monteverdi's first fifteen years of service in Mantua are bracketed by his publications of the third book of madrigals in 1592 and the fourth and fifth books in 1603 and 1605. Between 1592 and 1603 he made minor contributions to other anthologies. How much he composed in this period is a matter of conjecture; his many duties in the Mantuan court may have limited his opportunities, but several of the madrigals that he published in the fourth and fifth books were written and performed during the 1590s, some figuring prominently in the Artusi controversy.

The third book shows strongly the increased influence of Wert, by that time Monteverdi's direct superior as maestro de capella at Mantua. Two poets dominate the collection: Tasso, whose lyrical poetry had figured prominently in the second book but is here represented through the more epic, heroic verses from Gerusalemme liberata, and Giovanni Battista Guarini, whose verses had appeared sporadically in Monteverdi's earlier publications, but form around half of the contents of the third book. Wert's influence is reflected in Monteverdi's forthrightly modern approach, and his expressive and chromatic settings of Tasso's verses. Of the Guarini settings, Chew writes: "The epigrammatic style ... closely matches a poetic and musical ideal of the period ... [and] often depends on strong, final cadential progressions, with or without the intensification provided by chains of suspended dissonances". Chew cites the setting of "Stracciami pur il core" as "a prime example of Monteverdi's irregular dissonance practice". Tasso and Guarini were both regular visitors to the Mantuan court; Monteverdi's association with them and his absorption of their ideas may have helped lay the foundations of his own approach to the musical dramas that he would create a decade later.

As the 1590s progressed, Monteverdi moved closer towards the form that he would identify in due course as the seconda pratica. Claude V. Palisca quotes the madrigal Ohimè, se tanto amate, published in the fourth book but written before 1600 – it is among the works attacked by Artusi – as a typical example of the composer's developing powers of invention. In this madrigal Monteverdi again departs from the established practice in the use of dissonance, by means of a vocal ornament Palisca describes as échappé. Monteverdi's daring use of this device is, says Palisca, "like a forbidden pleasure". In this and in other settings the poet's images were supreme, even at the expense of musical consistency.

The fourth book includes madrigals to which Artusi objected on the grounds of their "modernism". However, Ossi describes it as "an anthology of disparate works firmly rooted in the 16th century", closer in nature to the third book than to the fifth. Besides Tasso and Guarini, Monteverdi set to music verses by Rinuccini, Maurizio Moro (Sì ch'io vorrei morire) and Ridolfo Arlotti (Luci serene e chiare). There is evidence of the composer's familiarity with the works of Carlo Gesualdo, and with composers of the school of Ferrara such as Luzzaschi; the book was dedicated to a Ferrarese musical society, the Accademici Intrepidi.

The fifth book looks more to the future; for example, Monteverdi employs the concertato style with basso continuo (a device that was to become a typical feature in the emergent Baroque era), and includes a sinfonia (instrumental interlude) in the final piece. He presents his music through complex counterpoint and daring harmonies, although at times combining the expressive possibilities of the new music with traditional polyphony.

Aquilino Coppini drew much of the music for his sacred contrafacta of 1608 from Monteverdi's 3rd, 4th and 5th books of madrigals. In writing to a friend in 1609 Coppini commented that Monteverdi's pieces "require, during their performance, more flexible rests and bars that are not strictly regular, now pressing forward or abandoning themselves to slowing down [...] In them there is a truly wondrous capacity for moving the affections".

Opera and sacred music: 1607–1612
In Monteverdi's final five years' service in Mantua he completed the operas L'Orfeo (1607) and L'Arianna (1608), and wrote quantities of sacred music, including the Messa in illo tempore (1610) and also the collection known as Vespro della Beata Vergine which is often referred to as "Monteverdi's Vespers" (1610). He also published Scherzi musicale a tre voci (1607), settings of verses composed since 1599 and dedicated to the Gonzaga heir, Francesco. The vocal trio in the Scherzi comprises two sopranos and a bass, accompanied by simple instrumental ritornellos. According to Bowers the music "reflected the modesty of the prince's resources; it was, nevertheless, the earliest publication to associate voices and instruments in this particular way".

L'Orfeo

The opera opens with a brief trumpet toccata. The prologue of La musica (a figure representing music) is introduced with a ritornello by the strings, repeated often to represent the "power of music" – one of the earliest examples of an operatic leitmotif. Act 1 presents a pastoral idyll, the buoyant mood of which continues into Act 2. The confusion and grief which follow the news of Euridice's death are musically reflected by harsh dissonances and the juxtaposition of keys. The music remains in this vein until the act ends with the consoling sounds of the ritornello.

Act 3 is dominated by Orfeo's aria "Possente spirto e formidabil nume" by which he attempts to persuade Caronte to allow him to enter Hades. Monteverdi's vocal embellishments and virtuoso accompaniment provide what Tim Carter has described as "one of the most compelling visual and aural representations" in early opera. In Act 4 the warmth of Proserpina's singing on behalf of Orfeo is retained until Orfeo fatally "looks back". The brief final act, which sees Orfeo's rescue and metamorphosis, is framed by the final appearance of the ritornello and by a lively moresca that brings the audience back to their everyday world.

Throughout the opera Monteverdi makes innovative use of polyphony, extending the rules beyond the conventions which composers normally observed in fidelity to Palestrina. He combines elements of the traditional 16th-century madrigal with the new monodic style where the text dominates the music and sinfonias and instrumental ritornellos illustrate the action.

L'Arianna
The music for this opera is lost except for the Lamento d'Arianna, which was published in the sixth book in 1614 as a five-voice madrigal; a separate monodic version was published in 1623. In its operatic context the lament depicts Arianna's various emotional reactions to her abandonment: sorrow, anger, fear, self-pity, desolation and a sense of futility. Throughout, indignation and anger are punctuated by tenderness, until a descending line brings the piece to a quiet conclusion.

The musicologist Suzanne Cusick writes that Monteverdi "creat[ed] the lament as a recognizable genre of vocal chamber music and as a standard scene in opera ... that would become crucial, almost genre-defining, to the full-scale public operas of 17th-century Venice". Cusick observes how Monteverdi is able to match in music the "rhetorical and syntactical gestures" in the text of Ottavio Rinuccini. The opening repeated words "Lasciatemi morire" (Let me die) are accompanied by a dominant seventh chord which Ringer describes as "an unforgettable chromatic stab of pain". Ringer suggests that the lament defines Monteverdi's innovative creativity in a manner similar to that in which the Prelude and the Liebestod in Tristan und Isolde announced Wagner's discovery of new expressive frontiers.

Rinuccini's full libretto, which has survived, was set in modern times by Alexander Goehr (Arianna, 1995), including a version of Monteverdi's Lament.

Vespers

The Vespro della Beata Vergine, Monteverdi's first published sacred music since the Madrigali spirituali of 1583, consists of 14 components: an introductory versicle and response, five psalms interspersed with five "sacred concertos" (Monteverdi's term), a hymn, and two Magnificat settings. Collectively these pieces fulfil the requirements for a Vespers  service on any feast day of the Virgin. Monteverdi employs many musical styles; the more traditional features, such as cantus firmus, falsobordone and Venetian canzone, are mixed with the latest madrigal style, including echo effects and chains of dissonances. Some of the musical features used are reminiscent of L'Orfeo, written slightly earlier for similar instrumental and vocal forces.

In this work the "sacred concertos" fulfil the role of the antiphons which divide the psalms in regular Vespers services. Their non-liturgical character has led writers to question whether they should be within the service, or indeed whether this was Monteverdi's intention. In some versions of Monteverdi's Vespers (for example, those of Denis Stevens) the concertos are replaced with antiphons associated with the Virgin, although John Whenham in his analysis of the work argues that the collection as a whole should be regarded as a single liturgical and artistic entity.

All the psalms, and the Magnificat, are based on melodically limited and repetitious Gregorian chant psalm tones, around which Monteverdi builds a range of innovative textures. This concertato style challenges the traditional cantus firmus, and is most evident in the "Sonata sopra Sancta Maria", written for eight string and wind instruments plus basso continuo, and a single soprano voice. Monteverdi uses modern rhythms, frequent metre changes and constantly varying textures; yet, according to John Eliot Gardiner, "for all the virtuosity of its instrumental writing and the evident care which has gone into the combinations of timbre", Monteverdi's chief concern was resolving the proper combination of words and music.

The actual musical ingredients of the Vespers were not novel to Mantua – concertato had been used by Lodovico Grossi da Viadana, a former choirmaster at the cathedral of Mantua, while the Sonata sopra had been anticipated by Archangelo Crotti in his Sancta Maria published in 1608. It is, writes Denis Arnold, Monteverdi's mixture of the various elements that makes the music unique. Arnold adds that the Vespers achieved fame and popularity only after their 20th-century rediscovery; they were not particularly regarded in Monteverdi's time.

Sixth book
During his years in Venice Monteverdi published his sixth (1614), seventh (1619) and eighth (1638) books of madrigals. The sixth book consists of works written before the composer's departure from Mantua. Hans Redlich sees it as a transitional work, containing Monteverdi's last madrigal compositions in the manner of the prima pratica, together with music which is typical of the new style of expression which Monteverdi had displayed in the dramatic works of 1607–08. The central theme of the collection is loss; the best-known work is the five-voice version of the Lamento d'Arianna, which, says Massimo Ossi, gives "an object lesson in the close relationship between monodic recitative and counterpoint". The book contains Monteverdi's first settings of verses by Giambattista Marino, and two settings of Petrarch which Ossi considers the most extraordinary pieces in the volume, providing some "stunning musical moments".

Seventh book
While Monteverdi had looked backwards in the sixth book, he moved forward in the seventh book from the traditional concept of the madrigal, and from monody, in favour of chamber duets. There are exceptions, such the two solo lettere amorose (love letters) "Se i languidi miei sguardi" and "Se pur destina e vole", written to be performed genere rapresentativo – acted as well as sung. Of the duets which are the main features of the volume, Chew highlights "Ohimé, dov'è il mio ben, dov'è il mio core", a romanesca in which two high voices express dissonances above a repetitive bass pattern. The book also contains large-scale ensemble works, and the ballet Tirsi e Clori. This was the height of Monteverdi's "Marino period"; six of the pieces in the book are settings of the poet's verses. As Carter puts it, Monteverdi "embraced Marino's madrigalian kisses and love-bites with ... the enthusiasm typical of the period". Some commentators have opined that the composer should have had better poetic taste.

Eighth book
The eighth book, subtitled Madrigali guerrieri, et amorosi ... ("Madrigals of war and love") is structured in two symmetrical halves, one for "war" and one for "love". Each half begins with a six-voice setting, followed by an equally large-scale Petrarch setting, then a series of duets mainly for tenor voices, and concludes with a theatrical number and a final ballet. The "war" half contains several items written as tributes to the emperor Ferdinand III, who had succeeded to the Habsburg throne in 1637. Many of Monteverdi's familiar poets – Strozzi, Rinuccini, Tasso, Marino, Guarini – are represented in the settings.

It is difficult to gauge when many of the pieces were composed, although the ballet Mascherata dell' ingrate that ends the book dates back to 1608 and the celebration of the Gonzaga-Savoy marriage. The Combattimento di Tancredi e Clorinda, centrepiece of the "war" settings, had been written and performed in Venice in 1624; on its publication in the eighth book, Monteverdi explicitly linked it to his concept of concitato genera (otherwise stile concitato – "aroused style") that would "fittingly imitate the utterance and the accents of a brave man who is engaged in warfare", and implied that since he had originated this style, others had begun to copy it. The work employed for the first time instructions for the use of pizzicato string chords, and also evocations of fanfares and other sounds of combat.

The critic Andrew Clements describes the eighth book as "a statement of artistic principles and compositional authority", in which Monteverdi "shaped and expanded the madrigal form to accommodate what he wanted to do ... the pieces collected in Book Eight make up a treasury of what music in the first half the 17th century could possibly express."

Other Venetian music: 1614–1638

During this period of his Venetian residency, Monteverdi composed quantities of sacred music. Numerous motets and other short works were included in anthologies by local publishers such as Giulio Cesare Bianchi (a former student of Monteverdi) and Lorenzo Calvi, and others were published elsewhere in Italy and Austria. The range of styles in the motets is broad, from simple strophic arias with string accompaniment to full-scale declamations with an alleluia finale.

Monteverdi retained emotional and political attachments to the Mantuan court and wrote for it, or undertook to write, large amounts of stage music including at least four operas. The ballet Tirsi e Clori survives through its inclusion in the seventh book, but the rest of the Mantuan dramatic music is lost. Many of the missing manuscripts may have disappeared in the wars that overcame Mantua in 1630. The most significant aspect of their loss, according to Carter, is the extent to which they might have provided musical links between Monteverdi's early Mantuan operas and those he wrote in Venice after 1638: "Without these links ... it is hard to a produce a coherent account of his development as a composer for the stage". Likewise, Janet Beat regrets that the 30-year gap hampers the study of how opera orchestration developed during those critical early years.

Apart from the madrigal books, Monteverdi's only published collection during this period was the volume of Scherzi musicale in 1632. For unknown reasons, the composer's name does not appear on the inscription, the dedication being signed by the Venetian printer Bartolomeo Magni; Carter surmises that the recently ordained Monteverdi may have wished to keep his distance from this secular collection. It mixes strophic continuo songs for solo voice with more complex works which employ continuous variation over repeated bass patterns. Chew selects the chaconne for two tenors, Zefiro torna e di soavi accenti, as the outstanding item in the collection: "[T]he greater part of this piece consists of repetitions of a bass pattern which ensures tonal unity of a simple kind, owing to its being framed as a simple cadence in a G major tonal type: over these repetitions, inventive variations unfold in virtuoso passage-work".

Late operas and final works
Main articles: Il ritorno d'Ulisse in patria; L'incoronazione di Poppea; Selva morale e spirituale

The last years of Monteverdi's life were much occupied with opera for the Venetian stage. Richard Taruskin, in his Oxford History of Western Music, gave his chapter on this topic the title "Opera from Monteverdi to Monteverdi." This wording, originally proposed humorously by the Italian music historian Nino Pirrotta, is interpreted seriously by Taruskin as indicating that Monteverdi is significantly responsible for the transformation of the opera genre from a private entertainment of the nobility (as with Orfeo in 1607), to what became a major commercial genre, as exemplified by his opera L'incoronazione di Poppea (1643). His two surviving operatic works of this period, Il ritorno d'Ulisse in patria and L'incoronazione are held by Arnold to be the first "modern" operas; Il ritorno is the first Venetian opera to depart from what Ellen Rosand terms "the mythological pastoral". However, David Johnson in the North American Review warns audiences not to expect immediate affinity with Mozart, Verdi or Puccini: "You have to submit yourself to a much slower pace, to a much more chaste conception of melody, to a vocal style that is at first merely like dry declamation and only on repeated hearings begins to assume an extraordinary eloquence."

Il ritorno, says Carter, is clearly influenced by Monteverdi's earlier works. Penelope's lament in Act I is close in character to the lament from L'Arianna, while the martial episodes recall Il combattimento. Stile concitato is prominent in the fight scenes and in the slaying of Penelope's suitors. In L'incoronazione, Monteverdi represents moods and situations by specific musical devices: triple metre stands for the language of love; arpeggios demonstrate conflict; stile concitato represents rage. There is continuing debate about how much of the extant L'incoronazione music is Monteverdi's original, and how much is the work of others (there are, for instance, traces of music by Francesco Cavalli).

The Selva morale e spirituale of 1641, and the posthumous Messa et salmi published in 1650 (which was edited by Cavalli), are selections of the sacred music that Monteverdi wrote for San Marco during his 30-year tenure – much else was likely written but not published. The Selva morale volume opens with a series of madrigal settings on moral texts, dwelling on themes such as "the transitory nature of love, earthly rank and achievement, even existence itself". They are followed by a Mass in conservative style (stile antico), the high point of which is an extended seven-voice "Gloria". Scholars believe that this might have been written to celebrate the end of the 1631 plague. The rest of the volume is made up of numerous psalm settings, two Magnificats and three Salve Reginas. The Messa et salmi volume includes a stile antico Mass for four voices, a polyphonic setting of the psalm Laetatus Sum, and a version of the Litany of Lareto that Monteverdi had originally published in 1620.

The posthumous ninth book of madrigals was published in 1651, a miscellany dating back to the early 1630s, some items being repeats of previously published pieces, such as the popular duet O sia tranquillo il mare from 1638. The book includes a trio for three sopranos, "Come dolce oggi l'auretta", which is the only surviving music from the 1630 lost opera Proserpina rapita.

Historical perspective
In his lifetime Monteverdi enjoyed considerable status among musicians and the public. This is evidenced by the scale of his funeral rites: "[W]ith truly royal pomp a catafalque was erected in the Chiesa de Padrini Minori de Frari, decorated all in mourning, but surrounded with so many candles that the church resembled a night sky luminous with stars". This glorification was transitory; Carter writes that in Monteverdi's day, music rarely survived beyond the circumstances of its initial performance and was quickly forgotten along with its creator. In this regard Monteverdi fared better than most. His operatic works were revived in several cities in the decade following his death; according to Severo Bonini, writing in 1651, every musical household in Italy possessed a copy of the Lamento d'Arianna.

The German composer Heinrich Schütz, who had studied in Venice under Giovanni Gabrieli shortly before Monteverdi's arrival there, possessed a copy of Il combattimento and himself took up elements of the stile concitato. On his second visit to Venice in 1628–1629, Arnold believes, Schütz absorbed the concepts of basso continuo and expressiveness of word-setting, but he opines that Schütz was more directly influenced by the style of the younger generation of Venetian composers, including Grandi and Giovanni Rovetta (the eventual successor to Monteverdi at San Marco). Schütz published a first book of Symphoniae sacrae, settings of biblical texts in the style of seconda pratica, in Venice in 1629. Es steh Gott auf, from his Symphoniae sacrae II, published in Dresden in 1647, contains specific quotations from Monteverdi.

After the 1650s, Monteverdi's name quickly disappears from contemporary accounts, his music generally forgotten except for the Lamento, the prototype of a genre that would endure well into the 18th century.

Interest in Monteverdi revived in the late 18th and early 19th centuries among music scholars in Germany and Italy, although he was still regarded as essentially a historical curiosity. Wider interest in the music itself began in 1881, when Robert Eitner published a shortened version of the Orfeo score. Around this time Kurt Vogel scored the madrigals from the original manuscripts, but more critical interest was shown in the operas, following the discovery of the L'incoronazione manuscript in 1888 and that of Il ritorno in 1904. Largely through the efforts of Vincent d'Indy, all three operas were staged in one form or another, during the first quarter of the 20th century: L'Orfeo in May 1911, L'incoronazione in February 1913 and Il ritorno in May 1925.

The Italian nationalist poet Gabriele D'Annunzio lauded Monteverdi and in his novel Il fuoco (1900) wrote of "il divino Claudio ... what a heroic soul, purely Italian in its essence!" His vision of Monteverdi as the true founder of Italian musical lyricism was adopted by musicians who worked with the regime of Benito Mussolini (1922–1945), including Gian Francesco Malipiero, Luigi Dallapiccola, and Mario Labroca, who contrasted Monteverdi with the decadence of the music of Richard Strauss, Claude Debussy and Igor Stravinsky.

In the years after the Second World War the operas began to be performed in the major opera houses, and eventually were established in the general repertory. The resuscitation of Monteverdi's sacred music took longer; he did not benefit from the Catholic Church's 19th-century revival of Renaissance music in the way that Palestrina did, perhaps, as Carter suggests, because Monteverdi was viewed chiefly as a secular composer. It was not until 1932 that the 1610 Vespers were published in a modern edition, followed by Redlich's revision two years later. Modern editions of the Selva morale and Missa e Salmi volumes were published respectively in 1940 and 1942.

The revival of public interest in Monteverdi's music gathered pace in the second half of the 20th century, reaching full spate in the general early-music revival of the 1970s, during which time the emphasis turned increasingly towards "authentic" performance using historical instruments. The magazine Gramophone notes over 30 recordings of the Vespers between 1976 and 2011, and 27 of Il combattimento di Tancredi e Clorinda between 1971 and 2013. Monteverdi's surviving operas are today regularly performed; the website Operabase notes 555 performances of the operas in 149 productions worldwide in the seasons 2011–2016, ranking Monteverdi at 30th position for all composers, and at 8th ranking for Italian opera composers. In 1985, Manfred H. Stattkus published an index to Monteverdi's works, the Stattkus-Verzeichnis, (revised in 2006) giving each composition an "SV" number, to be used for cataloguing and references.

Monteverdi is lauded by modern critics as "the most significant composer in late Renaissance and early Baroque Italy"; "one of the principal composers in the history of Western music"; and, routinely, as the first great opera composer. These assessments reflect a contemporary perspective, since his music was largely unknown to the composers who followed him during an extensive period, spanning more than two centuries after his death. It is, as Redlich and others have pointed out, the composers of the 20th and 21st century who have rediscovered Monteverdi and sought to make his music a basis for their own. Possibly, as Chew suggests, they are attracted by Monteverdi's reputation as "a Modern, a breaker of rules, against the Ancients, those who deferred to ancient authority" – although the composer was, essentially, a pragmatist, "showing what can only be described as an opportunistic and eclectic willingness to use whatever lay to hand for the purpose". In a letter dated 16 October 1633, Monteverdi appears to endorse the view of himself as a "modern": "I would rather be moderately praised for the new style than greatly praised for the ordinary". However, Chew, in his final summation, sees the composer historically as facing both ways, willing to use modern techniques but while at the same time protective of his status as a competent composer in the stile antico. Thus, says Chew, "his achievement was both retrospective and progressive". Monteverdi represents the late Renaissance era while simultaneously summing up much of the early Baroque. "And in one respect in particular, his achievement was enduring: the effective projection of human emotions in music, in a way adequate for theatre as well as for chamber music."

title: Claudio Monteverdi


text:
Colossus computer

Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves (vacuum tubes) to perform Boolean and counting operations. Colossus is thus regarded as the world's first programmable, electronic, digital computer, although it was programmed by switches and plugs and not by a stored program.

Colossus was designed by General Post Office (GPO) research telephone engineer Tommy Flowers based on plans developed by mathematician Max Newman at the Government Code and Cypher School (GC&CS) at Bletchley Park.

Alan Turing's use of probability in cryptanalysis (see Banburismus) contributed to its design. It has sometimes been erroneously stated that Turing designed Colossus to aid the cryptanalysis of the Enigma. (Turing's machine that helped decode Enigma was the electromechanical Bombe, not Colossus.)

The prototype, Colossus Mark 1, was shown to be working in December 1943 and was in use at Bletchley Park by early 1944. An improved Colossus Mark 2 that used shift registers to quintuple the processing speed, first worked on 1 June 1944, just in time for the Normandy landings on D-Day. Ten Colossi were in use by the end of the war and an eleventh was being commissioned. Bletchley Park's use of these machines allowed the Allies to obtain a vast amount of high-level military intelligence from intercepted radiotelegraphy messages between the German High Command (OKW) and their army commands throughout occupied Europe.

The existence of the Colossus machines was kept secret until the mid-1970s. All but two machines were dismantled into such small parts that their use could not be inferred. The two retained machines were eventually dismantled in the 1960s. In January 2024, new photos were released by GCHQ that showed re-engineered Colossus in a very different environment from the Bletchley Park buildings, presumably at GCHQ Cheltenham. A functioning reconstruction of a Mark 2 Colossus was completed in 2008 by Tony Sale and a team of volunteers; it is on display in The National Museum of Computing at Bletchley Park.

Purpose and origins

The Colossus computers were used to help decipher intercepted radio teleprinter messages that had been encrypted using an unknown device. Intelligence information revealed that the Germans called the wireless teleprinter transmission systems "Sägefisch" (sawfish). This led the British to call encrypted German teleprinter traffic "Fish", and the unknown machine and its intercepted messages "Tunny" (tunafish).

Before the Germans increased the security of their operating procedures, British cryptanalysts diagnosed how the unseen machine functioned and built an imitation of it called "British Tunny".

It was deduced that the machine had twelve wheels and used a Vernam ciphering technique on message characters in the standard 5-bit ITA2 telegraph code. It did this by combining the plaintext characters with a stream of key characters using the XOR Boolean function to produce the ciphertext.

In August 1941, a blunder by German operators led to the transmission of two versions of the same message with identical machine settings. These were intercepted and worked on at Bletchley Park. First, John Tiltman, a very talented GC&CS cryptanalyst, derived a keystream of almost 4000 characters. Then Bill Tutte, a newly arrived member of the Research Section, used this keystream to work out the logical structure of the Lorenz machine. He deduced that the twelve wheels consisted of two groups of five, which he named the χ (chi) and ψ (psi) wheels, the remaining two he called μ (mu) or "motor" wheels. The chi wheels stepped regularly with each letter that was encrypted, while the psi wheels stepped irregularly, under the control of the motor wheels.

With a sufficiently random keystream, a Vernam cipher removes the natural language property of a plaintext message of having an uneven frequency distribution of the different characters, to produce a uniform distribution in the ciphertext. The Tunny machine did this well. However, the cryptanalysts worked out that by examining the frequency distribution of the character-to-character changes in the ciphertext, instead of the plain characters, there was a departure from uniformity which provided a way into the system. This was achieved by "differencing" in which each bit or character was XOR-ed with its successor. After Germany surrendered, allied forces captured a Tunny machine and discovered that it was the electromechanical Lorenz SZ (Schlüsselzusatzgerät, cipher attachment) in-line cipher machine.

In order to decrypt the transmitted messages, two tasks had to be performed. The first was "wheel breaking", which was the discovery of the cam patterns for all the wheels. These patterns were set up on the Lorenz machine and then used for a fixed period of time for a succession of different messages. Each transmission, which often contained more than one message, was enciphered with a different start position of the wheels. Alan Turing invented a method of wheel-breaking that became known as Turingery. Turing's technique was further developed into "Rectangling", for which Colossus could produce tables for manual analysis. Colossi 2, 4, 6, 7 and 9 had a "gadget" to aid this process.

The second task was "wheel setting", which worked out the start positions of the wheels for a particular message and could only be attempted once the cam patterns were known. It was this task for which Colossus was initially designed. To discover the start position of the chi wheels for a message, Colossus compared two character streams, counting statistics from the evaluation of programmable Boolean functions. The two streams were the ciphertext, which was read at high speed from a paper tape, and the keystream, which was generated internally, in a simulation of the unknown German machine. After a succession of different Colossus runs to discover the likely chi-wheel settings, they were checked by examining the frequency distribution of the characters in the processed ciphertext. Colossus produced these frequency counts.

Decryption processes
By using differencing and knowing that the psi wheels did not advance with each character, Tutte worked out that trying just two differenced bits (impulses) of the chi-stream against the differenced ciphertext would produce a statistic that was non-random. This became known as Tutte's "1+2 break in". It involved calculating the following Boolean function:
 * $$\Delta Z_1 \oplus \Delta Z_2 \oplus \Delta\chi_1 \oplus \Delta\chi_2 = \bullet$$

and counting the number of times it yielded "false" (zero). If this number exceeded a pre-defined threshold value known as the "set total", it was printed out. The cryptanalyst would examine the printout to determine which of the putative start positions was most likely to be the correct one for the chi-1 and chi-2 wheels.

This technique would then be applied to other pairs of, or single, impulses to determine the likely start position of all five chi wheels. From this, the de-chi (D) of a ciphertext could be obtained, from which the psi component could be removed by manual methods. If the frequency distribution of characters in the de-chi version of the ciphertext was within certain bounds, "wheel setting" of the chi wheels was considered to have been achieved, and the message settings and de-chi were passed to the "Testery". This was the section at Bletchley Park led by Major Ralph Tester where the bulk of the decrypting work was done by manual and linguistic methods.

Colossus could also derive the start position of the psi and motor wheels. The feasibility of utilizing this additional capability regularly was made possible in the last few months of the war when there were plenty of Colossi available and the number of Tunny messages had declined.

Design and construction
Colossus was developed for the "Newmanry", the section headed by the mathematician Max Newman that was responsible for machine methods against the twelve-rotor Lorenz SZ40/42 on-line teleprinter cipher machine (code-named Tunny, for tunafish). The Colossus design arose out of a parallel project that produced a less-ambitious counting machine dubbed "Heath Robinson". Although the Heath Robinson machine proved the concept of machine analysis for this part of the process, it had serious limitations. The electro-mechanical parts were relatively slow and it was difficult to synchronise two looped paper tapes, one containing the enciphered message, and the other representing part of the keystream of the Lorenz machine. Also the tapes tended to stretch and break when being read at up to 2000 characters per second.

Tommy Flowers MBE was a senior electrical engineer and Head of the Switching Group at the Post Office Research Station at Dollis Hill. Prior to his work on Colossus, he had been involved with GC&CS at Bletchley Park from February 1941 in an attempt to improve the Bombes that were used in the cryptanalysis of the German Enigma cipher machine. He was recommended to Max Newman by Alan Turing, who had been impressed by his work on the Bombes. The main components of the Heath Robinson machine were as follows.
 * A tape transport and reading mechanism that ran the looped key and message tapes at between 1000 and 2000 characters per second.
 * A combining unit that implemented the logic of Tutte's method.
 * A counting unit that had been designed by C. E. Wynn-Williams of the Telecommunications Research Establishment (TRE) at Malvern, which counted the number of times the logical function returned a specified truth value.

Flowers had been brought in to design the Heath Robinson's combining unit. He was not impressed by the system of a key tape that had to be kept synchronised with the message tape and, on his own initiative, he designed an electronic machine which eliminated the need for the key tape by having an electronic analogue of the Lorenz (Tunny) machine. He presented this design to Max Newman in February 1943, but the idea that the one to two thousand thermionic valves (vacuum tubes and thyratrons) proposed, could work together reliably, was greeted with great scepticism, so more Robinsons were ordered from Dollis Hill. Flowers, however, knew from his pre-war work that most thermionic valve failures occurred as a result of the thermal stresses at power-up, so not powering a machine down reduced failure rates to very low levels. Additionally, if the heaters were started at a low voltage then slowly brought up to full voltage, thermal stress was reduced. The valves themselves could be soldered-in to avoid problems with plug-in bases, which could be unreliable. Flowers persisted with the idea and obtained support from the Director of the Research Station, W Gordon Radley.

Flowers and his team of some fifty people in the switching group spent eleven months from early February 1943 designing and building a machine that dispensed with the second tape of the Heath Robinson, by generating the wheel patterns electronically. Flowers used some of his own money for the project. This prototype, Mark 1 Colossus, contained 1,600 thermionic valves (tubes). It performed satisfactorily at Dollis Hill on 8 December 1943 and was dismantled and shipped to Bletchley Park, where it was delivered on 18 January and re-assembled by Harry Fensom and Don Horwood. It was operational in January and it successfully attacked its first message on 5 February 1944. It was a large structure and was dubbed 'Colossus'. A memo held in the National Archives written by Max Newman on 18 January 1944 records that "Colossus arrives today".

During the development of the prototype, an improved design had been developed – the Mark 2 Colossus. Four of these were ordered in March 1944 and by the end of April the number on order had been increased to twelve. Dollis Hill was put under pressure to have the first of these working by 1 June. Allen Coombs took over leadership of the production Mark 2 Colossi, the first of which – containing 2,400 valves – became operational at 08:00 on 1 June 1944, just in time for the Allied Invasion of Normandy on D-Day. Subsequently, Colossi were delivered at the rate of about one a month. By the time of V-E Day there were ten Colossi working at Bletchley Park and a start had been made on assembling an eleventh. Seven of the Colossi were used for 'wheel setting' and three for 'wheel breaking'.

The main units of the Mark 2 design were as follows.
 * A tape transport with an 8-photocell reading mechanism.
 * A six character FIFO shift register.
 * Twelve thyratron ring stores that simulated the Lorenz machine generating a bit-stream for each wheel.
 * Panels of switches for specifying the program and the "set total".
 * A set of functional units that performed Boolean operations.
 * A "span counter" that could suspend counting for part of the tape.
 * A master control that handled clocking, start and stop signals, counter readout and printing.
 * Five electronic counters.
 * An electric typewriter.

Most of the design of the electronics was the work of Tommy Flowers, assisted by William Chandler, Sidney Broadhurst and Allen Coombs; with Erie Speight and Arnold Lynch developing the photoelectric reading mechanism. Coombs remembered Flowers, having produced a rough draft of his design, tearing it into pieces that he handed out to his colleagues for them to do the detailed design and get their team to manufacture it. The Mark 2 Colossi were both five times faster and were simpler to operate than the prototype.

Data input to Colossus was by photoelectric reading of a paper tape transcription of the enciphered intercepted message. This was arranged in a continuous loop so that it could be read and re-read multiple times – there being no internal storage for the data. The design overcame the problem of synchronizing the electronics with the speed of the message tape by generating a clock signal from reading its sprocket holes. The speed of operation was thus limited by the mechanics of reading the tape. During development, the tape reader was tested up to 9700 characters per second (53 mph) before the tape disintegrated. So 5000 characters/second (40 ft/s) was settled on as the speed for regular use. Flowers designed a 6-character shift register, which was used both for computing the delta function (ΔZ) and for testing five different possible starting points of Tunny's wheels in the five processors. This five-way parallelism enabled five simultaneous tests and counts to be performed giving an effective processing speed of 25,000 characters per second. The computation used algorithms devised by W. T. Tutte and colleagues to decrypt a Tunny message.

Operation
The Newmanry was staffed by cryptanalysts, operators from the Women's Royal Naval Service (WRNS) – known as "Wrens" – and engineers who were permanently on hand for maintenance and repair. By the end of the war the staffing was 272 Wrens and 27 men.

The first job in operating Colossus for a new message was to prepare the paper tape loop. This was performed by the Wrens who stuck the two ends together using Bostik glue, ensuring that there was a 150-character length of blank tape between the end and the start of the message. Using a special hand punch they inserted a start hole between the third and fourth channels $2 1/2$ sprocket holes from the end of the blank section, and a stop hole between the fourth and fifth channels $1 1/2$ sprocket holes from the end of the characters of the message. These were read by specially positioned photocells and indicated when the message was about to start and when it ended. The operator would then thread the paper tape through the gate and around the pulleys of the bedstead and adjust the tension. The two-tape bedstead design had been carried on from Heath Robinson so that one tape could be loaded whilst the previous one was being run. A switch on the Selection Panel specified the "near" or the "far" tape.

After performing various resetting and zeroizing tasks, the Wren operators would, under instruction from the cryptanalyst, operate the "set total" decade switches and the K2 panel switches to set the desired algorithm. They would then start the bedstead tape motor and lamp and, when the tape was up to speed, operate the master start switch.

Programming
Howard Campaigne, a mathematician and cryptanalyst from the US Navy's OP-20-G, wrote the following in a foreword to Flowers' 1983 paper "The Design of Colossus"."My view of Colossus was that of cryptanalyst-programmer. I told the machine to make certain calculations and counts, and after studying the results, told it to do another job. It did not remember the previous result, nor could it have acted upon it if it did. Colossus and I alternated in an interaction that sometimes achieved an analysis of an unusual German cipher system, called 'Geheimschreiber' by the Germans, and 'Fish' by the cryptanalysts."

Colossus was not a stored-program computer. The input data for the five parallel processors was read from the looped message paper tape and the electronic pattern generators for the chi, psi and motor wheels. The programs for the processors were set and held on the switches and jack panel connections. Each processor could evaluate a Boolean function and count and display the number of times it yielded the specified value of "false" (0) or "true" (1) for each pass of the message tape.

Input to the processors came from two sources, the shift registers from tape reading and the thyratron rings that emulated the wheels of the Tunny machine. The characters on the paper tape were called Z and the characters from the Tunny emulator were referred to by the Greek letters that Bill Tutte had given them when working out the logical structure of the machine. On the selection panel, switches specified either Z or ΔZ, either $$\chi$$ or Δ$$\chi$$ and either $$\psi$$ or Δ$$\psi$$ for the data to be passed to the jack field and 'K2 switch panel'. These signals from the wheel simulators could be specified as stepping on with each new pass of the message tape or not.

The K2 switch panel had a group of switches on the left-hand side to specify the algorithm. The switches on the right-hand side selected the counter to which the result was fed. The plugboard allowed less specialized conditions to be imposed. Overall the K2 switch panel switches and the plugboard allowed about five billion different combinations of the selected variables.

As an example: a set of runs for a message tape might initially involve two chi wheels, as in Tutte's 1+2 algorithm. Such a two-wheel run was called a long run, taking on average eight minutes unless the parallelism was utilised to cut the time by a factor of five. The subsequent runs might only involve setting one chi wheel, giving a short run taking about two minutes. Initially, after the initial long run, the choice of the next algorithm to be tried was specified by the cryptanalyst. Experience showed, however, that decision trees for this iterative process could be produced for use by the Wren operators in a proportion of cases.

Influence and fate
Although the Colossus was the first of the electronic digital machines with programmability, albeit limited by modern standards, it was not a general-purpose machine, being designed for a range of cryptanalytic tasks, most involving counting the results of evaluating Boolean algorithms.

A Colossus computer was thus not a fully Turing complete machine. However, University of San Francisco professor Benjamin Wells has shown that if all ten Colossus machines made were rearranged in a specific cluster, then the entire set of computers could have simulated a universal Turing machine, and thus be Turing complete.

Colossus and the reasons for its construction were highly secret and remained so for 30 years after the War. Consequently, it was not included in the history of computing hardware for many years, and Flowers and his associates were deprived of the recognition they were due. All but two of the Colossi were dismantled after the war and parts returned to the Post Office. Some parts, sanitised as to their original purpose, were taken to Max Newman's Royal Society Computing Machine Laboratory at Manchester University. Two Colossi, along with two Tunny machines, were retained and moved to GCHQ's new headquarters at Eastcote in April 1946, and then to Cheltenham between 1952 and 1954. One of the Colossi, known as Colossus Blue, was dismantled in 1959; the other in the 1960s. Tommy Flowers was ordered to destroy all documentation. He duly burnt them in a furnace and later said of that order: "That was a terrible mistake. I was instructed to destroy all the records, which I did. I took all the drawings and the plans and all the information about Colossus on paper and put it in the boiler fire. And saw it burn."The Colossi were adapted for other purposes, with varying degrees of success; in their later years they were used for training. Jack Good related how he was the first to use Colossus after the war, persuading the US National Security Agency that it could be used to perform a function for which they were planning to build a special-purpose machine. Colossus was also used to perform character counts on one-time pad tape to test for non-randomness.

A small number of people who were associated with Colossus—and knew that large-scale, reliable, high-speed electronic digital computing devices were feasible—played significant roles in early computer work in the UK and probably in the US. However, being so secret, it had little direct influence on the development of later computers; it was EDVAC that was the seminal computer architecture of the time. In 1972, Herman Goldstine, who was unaware of Colossus and its legacy to the projects of people such as Alan Turing (ACE), Max Newman (Manchester computers) and Harry Huskey (Bendix G-15), wrote that,

"Britain had such vitality that it could immediately after the war embark on so many well-conceived and well-executed projects in the computer field."

Professor Brian Randell, who unearthed information about Colossus in the 1970s, commented on this, saying that: "It is my opinion that the COLOSSUS project was an important source of this vitality, one that has been largely unappreciated, as has the significance of its places in the chronology of the invention of the digital computer."

Randell's efforts started to bear fruit in the mid-1970s. The secrecy about Bletchley Park had been broken when Group Captain Winterbotham published his book The Ultra Secret in 1974. Randell was researching the history of computer science in Britain for a conference on the history of computing held at the Los Alamos Scientific Laboratory, New Mexico on 10–15 June 1976, and got permission to present a paper on wartime development of the COLOSSI at the Post Office Research Station,  Dollis Hill (in October 1975 the British Government had released a series of captioned photographs from the Public Record Office). The interest in the "revelations" in his paper resulted in a special evening meeting when Randell and Coombs answered further questions. Coombs later wrote that no member of our team could ever forget the fellowship, the sense of purpose and, above all, the breathless excitement of those days. In 1977 Randell published an article The First Electronic Computer in several journals.

In October 2000, a 500-page technical report on the Tunny cipher and its cryptanalysis—entitled General Report on Tunny—was released by GCHQ to the national Public Record Office, and it contains a fascinating paean to Colossus by the cryptographers who worked with it: "It is regretted that it is not possible to give an adequate idea of the fascination of a Colossus at work; its sheer bulk and apparent complexity; the fantastic speed of thin paper tape round the glittering pulleys; the childish pleasure of not-not, span, print main header and other gadgets; the wizardry of purely mechanical decoding letter by letter (one novice thought she was being hoaxed); the uncanny action of the typewriter in printing the correct scores without and beyond human aid; the stepping of the display; periods of eager expectation culminating in the sudden appearance of the longed-for score; and the strange rhythms characterizing every type of run: the stately break-in, the erratic short run, the regularity of wheel-breaking, the stolid rectangle interrupted by the wild leaps of the carriage-return, the frantic chatter of a motor run, even the ludicrous frenzy of hosts of bogus scores."

Reconstruction
A team led by Tony Sale built a fully functional reconstruction of a Colossus Mark 2 between 1993 and 2008. In spite of the blueprints and hardware being destroyed, a surprising amount of material had survived, mainly in engineers' notebooks, but a considerable amount of it in the U.S. The optical tape reader might have posed the biggest problem, but Dr. Arnold Lynch, its original designer was able to redesign it to his own original specification. The reconstruction is on display, in the historically correct place for Colossus No. 9, at The National Museum of Computing, in H Block Bletchley Park in Milton Keynes, Buckinghamshire.

In November 2007, to celebrate the project completion and to mark the start of a fundraising initiative for The National Museum of Computing, a Cipher Challenge pitted the rebuilt Colossus against radio amateurs worldwide in being first to receive and decode three messages enciphered using the Lorenz SZ42 and transmitted from radio station DL0HNF in the Heinz Nixdorf MuseumsForum computer museum. The challenge was easily won by radio amateur Joachim Schüth, who had carefully prepared for the event and developed his own signal processing and code-breaking code using Ada. The Colossus team were hampered by their wish to use World War II radio equipment, delaying them by a day because of poor reception conditions. Nevertheless, the victor's 1.4 GHz laptop, running his own code, took less than a minute to find the settings for all 12 wheels. The German codebreaker said: "My laptop digested ciphertext at a speed of 1.2 million characters per second—240 times faster than Colossus. If you scale the CPU frequency by that factor, you get an equivalent clock of 5.8 MHz for Colossus. That is a remarkable speed for a computer built in 1944."

The Cipher Challenge verified the successful completion of the rebuilding project. "On the strength of today's performance Colossus is as good as it was six decades ago", commented Tony Sale. "We are delighted to have produced a fitting tribute to the people who worked at Bletchley Park and whose brainpower devised these fantastic machines which broke these ciphers and shortened the war by many months."

Other meanings
There was a fictional computer named Colossus in the 1970 film Colossus: The Forbin Project which was based on the 1966 novel Colossus by D. F. Jones. This was a coincidence as it pre-dates the public release of information about Colossus, or even its name.

Neal Stephenson's novel Cryptonomicon (1999) also contains a fictional treatment of the historical role played by Turing and Bletchley Park.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Colossus computer


text:
Canadian Shield

The Canadian Shield (Bouclier canadien ), also called the Laurentian Shield or the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the ancient geologic core of the North American continent. Glaciation has left the area with only a thin layer of soil, through which exposures of igneous bedrock resulting from its long volcanic history are frequently visible. As a deep, common, joined bedrock region in eastern and central Canada, the shield stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada and most of Greenland; it also extends south into the northern reaches of the continental United States.

Geographical extent
The Canadian Shield is a physiographic division comprising four smaller physiographic provinces: the Laurentian Upland, Kazan Region, Davis and James. The shield extends into the United States as the Adirondack Mountains (connected by the Frontenac Axis) and the Superior Upland. The Canadian Shield is a U-shaped subsection of the Laurentia craton signifying the area of greatest glacial impact (scraping down to bare rock) creating the thin soils. The age of the Canadian Shield is estimated to be 4.28 Ga. The Canadian Shield once had jagged peaks, higher than any of today's mountains, but millions of years of erosion have changed these mountains to rolling hills.

The Canadian Shield is a collage of Archean plates and accreted juvenile arc terranes and sedimentary basins of the Proterozoic Eon that were progressively amalgamated during the interval 2.45–1.24 Ga, with the most substantial growth period occurring during the Trans-Hudson orogeny, between c. 1.90–1.80 Ga. The Canadian Shield was the first part of North America to be permanently elevated above sea level and has remained almost wholly untouched by successive encroachments of the sea upon the continent. It is the Earth's greatest area of exposed Archean rock. The metamorphic base rocks are mostly from the Precambrian (between 4.5 Ga and 540 Ma) and have been repeatedly uplifted and eroded. Today it consists largely of an area of low relief 300 – above sea level with a few monadnocks and low mountain ranges (including the Laurentian Mountains) probably eroded from the plateau during the Cenozoic Era. During the Pleistocene Epoch, continental ice sheets depressed the land surface (creating Hudson Bay) but also tilted up its northeastern "rim" (the Torngat), scooped out thousands of lake basins, and carried away much of the region's soil. The northeastern portion, however, became tilted up so that, in northern Labrador and Baffin Island, the land rises to more than 1,500 metres (5,000 feet) above sea level.

When the Greenland section is included, the Canadian Shield is approximately circular, bounded on the northeast by the northeast edge of Greenland, with Hudson Bay in the middle. It covers much of Greenland, all of Labrador and the Great Northern Peninsula of Newfoundland, most of Quebec north of the St. Lawrence River, much of Ontario including northern sections of the Ontario Peninsula, the Adirondack Mountains of New York, the northernmost part of Lower Michigan and all of Upper Michigan, northern Wisconsin, northeastern Minnesota, the central and northern portions of Manitoba, northern Saskatchewan, a small portion of northeastern Alberta, mainland Northwest Territories to the east of a line extended north from the Saskatchewan-Alberta border, most of Nunavut's mainland and, of its Arctic Archipelago, Baffin Island and significant bands through Somerset, Southampton, Devon and Ellesmere islands. In total, the exposed area of the shield covers approximately 8000000 km2. The true extent of the shield is greater still and stretches from the Western Cordillera in the west to the Appalachians in the east and as far south as Texas, but these regions are overlaid with much younger rocks and sediment.

Geology
The Canadian Shield is among the oldest on Earth, with regions dating from 2.5 to 4.2 billion years. The multitude of rivers and lakes in the region is classical example of a deranged drainage system, caused by the watersheds of the area being disturbed by glaciation and the effect of post-glacial rebound. The shield was originally an area of very large, very tall mountains (about 12000 m) with much volcanic activity, but the area was eroded to nearly its current topographic appearance of relatively low relief over 500 Ma. Erosion has exposed the roots of the mountains, which take the form of greenstone belts in which belts of volcanic rock that have been altered by metamorphism are surrounded by granitic rock. These belts range in age from 3.6 to 2.7 Ga. Much of the granitic rock belongs to the distinctive tonalite–trondhjemite–granodiorite family of rocks, which are characteristic of Archean continental crust. Many of Canada's major ore deposits are associated with greenstone belts.

The Sturgeon Lake Caldera in Kenora District, Ontario, is one of the world's best preserved mineralized Neoarchean caldera complexes, which is 2.7 Ga. The Canadian Shield also contains the Mackenzie dike swarm, which is the largest dike swarm known on Earth. The North American craton is the bedrock forming the heart of the North American continent, and the Canadian Shield is the largest exposed part of the craton's bedrock. The Canadian Shield is part of an ancient continent called Arctica, which was formed about 2.5 Ga during the Neoarchean era.

Mountains have deep roots and float on the denser mantle much like an iceberg at sea. As mountains erode, their roots rise and are eroded in turn. The rocks that now form the surface of the shield were once far below the Earth's surface. The high pressures and temperatures at those depths provided ideal conditions for mineralization. Although these mountains are now heavily eroded, many large mountains still exist in Canada's far north called the Arctic Cordillera. This is a vast, deeply dissected mountain range, stretching from northernmost Ellesmere Island to the northernmost tip of Labrador. The range's highest peak is Nunavut's Barbeau Peak at 2616 m above sea level. Precambrian rock is the major component of the bedrock.

Ecology

The current surface expression of the shield is one of very thin soil lying on top of the bedrock, with many bare outcrops. This arrangement was caused by severe glaciation during the ice ages that covered the shield and scraped the rock clean. The lowlands of the Canadian Shield have a very dense soil that is not suitable for forestation; it also contains many marshes and bogs (muskegs). The rest of the region has coarse soil that does not retain moisture well and is frozen with permafrost throughout the year. Forests are not as dense in the north.

The shield is covered in parts by vast boreal forests in the south that support natural ecosystems as well as a major logging industry. The boreal forest area gives way to the Eastern Canadian Shield taiga that covers northern Quebec and most of Labrador. The Midwestern Canadian Shield forests that run westwards from Northwestern Ontario have boreal forests that give way to taiga in the most northerly parts of Manitoba and Saskatchewan. Hydrologic drainage is generally poor, the soil compacting effects of glaciation being one of the many causes. Tundra typically prevails in the northern regions.

Many mammals such as beaver, caribou, white-tailed deer, moose, wolves, wolverines, weasels, mink, otters, grizzly bear, polar bears and black bears are present. In the case of polar bears (Ursus maritimus), the shield area contains many of their denning locations, such as the Wapusk National Park. The many lakes and rivers on the shield contain a plentiful quantity of different sports fish species, including walleye, northern pike, lake trout, yellow perch, whitefish, brook trout, arctic grayling, and many types of baitfish. The water surfaces are also home to many waterfowl, most notably Canada geese, loons and gulls. The vast forests contain a myriad population of other birds, including ravens and crows, predatory birds and many songbirds.

Mining and economics
The Canadian Shield is one of the world's richest areas in terms of mineral ores. It is filled with substantial deposits of nickel, gold, silver, and copper. There are many mining towns extracting these minerals. The largest, and one of the best known, is Sudbury, Ontario. Sudbury is an exception to the normal process of forming minerals in the shield since the Sudbury Basin is an ancient meteorite impact crater. Ejecta from the meteorite impact was found in the Rove Formation in May 2007. The nearby but less-known Temagami Magnetic Anomaly has striking similarities to the Sudbury Basin. This suggests it could be a second metal-rich impact crater. In northeastern Quebec, the giant Manicouagan Reservoir is the site of an extensive hydroelectric project (Manic-cinq, or Manic-5). This is one of the largest-known meteorite impact craters on Earth, though not as large as the Sudbury crater.

The Flin Flon greenstone belt in central Manitoba and east-central Saskatchewan "is one of the largest Paleoproterozoic volcanic-hosted massive sulfide (VMS) districts in the world, containing 27 copper-zinc-(gold) deposits from which more than 183 million tonnes of sulfide have been mined." The portion in the Northwest Territories has recently been the site of several major diamond discoveries. The kimberlite pipes in which the diamonds are found are closely associated with cratons, which provide the deep lithospheric mantle required to stabilize diamond as a mineral. The kimberlite eruptions then bring the diamonds from over 150 km depth to the surface. The Ekati and Diavik mines are actively mining kimberlite diamonds.

title: Canadian Shield