The initial idea of a new ballet for Balanchine cast in the form of a dance contest actually went back to 1948 and Stravinsky had begun writing it in the autumn of 1953. But over the next couple of years its progress was repeatedly interrupted by the composition of In Memoriam Dylan Thomas (with whom he had hoped to collaborate on an opera), the Canticum Sacrum and his orchestral re-composition of Bach's canonic variations on Vom Himmel Hoch. Then, shortly after conducting the world premiere of the Canticum Sacrum in St Mark's, Venice, in September 1956, Stravinsky suffered a near-fatal stroke and the final sections of Agon were completed in 1957 under its lasting after-effects.
Meanwhile, thanks to his ever acquisitive ear, his musical style had been steadily shifting over this protracted period from the contrapuntal modality of such works as his Cantata (1952), written in the wake of The Rake's Progress, to an overt 12-note serialism that was shortly to generate a full-length structure in his setting of the Lamentations of Jeremiah, Threni (1958).
The resulting 23 minutes of Agon, additionally splintered between no fewer than 18 dance numbers, threatened to prove the most disparate, magpie gathering of stylistic patches even Stravinsky had ever attempted to hold together, and neither he nor Balanchine seem to have anticipated that it would so rapidly establish itself in both the theatre and the concert hall as the most successful of all the late works. How to explain, then, that this perilous synthesis now comes over to us as arguably the central achievement of the musical 1950s?
More central, some might ask, than that self-conscious chef d'oeuvre of the post-war European avant-garde: Pierre Boulez's Le Marteau sans maitre (1956) with its twinkling textures now so curiously reminiscent of another quintessentially Fifties sound - the Modern Jazz Quartet? Or what about the pioneering deployment in Edgard Varese's Deserts (1954) of the decade's own newest medium, concrete sounds on tape? What indeed of the progressive traditionalism of so inexorably structured a music drama as Benjamin Britten's The Turn of the Screw (1954)? And, in any case, how could Stravinsky's crisp, elegant score - essentially a divertimento - be held to represent a period in which the over-arching problem was learning to live with an ever ominous Cold War tension between ideological blocs, each of them wielding power enough to wipe out humanity?
Those who were young then will recall how pervasive the conformist pressures, the fear, could be. In his autobiographical essay collection, Music and Politics, Hans Werner Henze has a symptomatic vignette from the Darmstadt summer school of 1955: "Boulez, who saw himself as the supreme authority, was sitting at the piano flanked by Maderna and myself - we must have looked like reluctant assistant judges at a trial, as young composers brought their pieces forward for opinion. Anything that wasn't Webernian, he briskly dismissed: 'If it isn't written in the style of Webern, it's of no interest.' " Difficult to avoid recalling not just Shostakovich's periodic humiliations by the Union of Soviet Composers, but Copland's 1953 arraignment before Senator McCarthy's merry men for his leftish leanings back in the Thirties.
Yet it is equally symptomatic that Boulez was brandishing the works of Webern, not Marx. Commentators on the Fifties have often noted a strangely a-political mood, as if people felt the world situation was too grim to contemplate, let alone take action over (that would have to wait till the Sixties). True, a number of composers, mostly of more traditional leanings, remained residually political in their desire to serve their communities: "I want my music to be of use to people," Britten was to claim. "I do not write for posterity - in any case, the outlook for that is somewhat uncertain." True, also, there were political spirits even among the avant-garde, but the stylistic difference between Luigi Nono's fiercely committed Il Canto Sospeso (1956) and Boulez's hyper-aesthetic Improvisations sur Mallarme (1958) would not have been so obvious to the ordinary listener. As for Darmstadt itself, it was as if energies normally expressed in politics had got entirely diverted into controversies about musical technique.
Yet it would be wrong to assume, as so many subsequent commentators have, that the musical life of the Fifties comprised no more than an avant-garde conspiracy to replace traditional values. Between, on the one hand, a variety of mostly conservative older figures - Vaughan Williams, Milhaud, Martinu, Shostakovich, Walton - who went on composing much as they always had and, on the other, the young Darmstadt followers of Boulez and Stockhausen who believed they were evolving a wholly new language, following a "zero" year around 1951, there ranged - not least in Britain - a wide variety of composers attempting in different ways to carry forward tradition, to absorb the innovations of such earlier moderns as Bartok and Schoenberg and even to adapt the odd innovation from the avant-garde itself. Simply to name Britten, Tippett, Lutyens, Copland, Carter, Wolpe, Dallapiccola, Gerhard, Lutoslawski and Henze is to recall just how rich the decade really was. And beyond even these, there were the originals: thanks partly to the rise of his pupils (who included Boulez and Stockhausen), Messiaen is often thought of as a central Fifties figure. Yet absolutely no one else was creating his sort of music out of birdsong.
So where did Stravinsky fit into all this? Essentially a religious rather than political being, he had always scorned the engage. But if his first commitment was to God, his second was to music, its substance and essence, in a way that far transcended the mere modishness he had so often been charged with. Granted his Fifties "conversion" to serialism, his new-found interest not only in Webern but in Boulez and Stockhausen could be construed that way. Yet he was equally alive to another development that the current instalment of Towards the Millennium ought perhaps to have reflected: due partly to a new generation of scholar-performers and partly to the advent of the long-playing record, the Fifties was the first decade in which early music really began to emerge from the academic closet.
Agon is ostensibly modelled on early 17th-century French court dances, but its procedures and allusions advance from neo-Medieval cadences by way of neo-Baroque rhythms to a Pas de deux sounding like Tchaikovsky re-composed by Webern, and even to a few jagged bars of neo-Boulez, before suddenly going backwards at the end.
Yet the characterisation of his sequence as a virtual history of music is only one of the means by which Stravinsky unifies this seemingly most disjunct of works. Early critics were equally alive to a kind of lateral synthesis between the most esoteric techniques and musical gestures obliquely redolent of jazz, vernacular song, even the street sounds of New York. And beneath the faceted surface, there runs an almost organic process as basic figures are passed to and fro between diatonic, chromatic and serial states. But most of all, in its reach, vitality and skill, the score affirms. And while affirmatory art always risks dismissal as irrelevant or escapist in a dark or uncertain age, one imagines only the most hidebound conservative or doctrinaire avant-gardist could ever cavil at the spirit of renewal so saliently embodied in Agon.
n Sir Simon Rattle conducts 'Agon' (with Messiaen's 'Chronochromie' and Stockhausen's 'Gruppen'): 7pm tomorrow, Symphony Hall, Birmingham and 7.30pm Sun, RFH, London (broadcast Wed on Radio 3)