The instigator was that most mordant of musical eccentrics, Erik Satie, who had positioned a number of players around the auditorium. The music he had devised for them to play was not, however, the kind of tuneful background stuff society had been used to chattering through at balls, cafe concerts, receptions and so on for centuries. Instead, it comprised a few dried-up cliches locked into endless cycles of abstract repetitions under the working title of musique d'ameublement, or 'furnishing music'. Alas, no sooner had the players launched into their aural wallpaper than a hush descended. 'Go on talking]' cried Satie. 'Walk about] Don't listen]' But it was no good. The audience seemed determined to treat what, if disregarded, would have amounted to an uncanny pre-echo of Muzak, with the attention still more recently accorded to the phenomenon of Minimalism. Yet the real question is whether Satie was quite so far ahead after all. The more one listens to, and thinks about the 1920s, the more one suspects the cultural confusions latterly lumped under the label Post-Modern had already begun to set in.
Granted, the notion of the 1920s as a uniquely hedonistic spree between the horrors of the First World War and the rise of fascism dies hard - even when one recalls that the period began with hyper-inflation in Germany, went on with the General Strike in Britain and culminated in the United States with the Great Crash of 1929. Granted, too, that the decade continued to be dominated by such composers as Schoenberg, Stravinsky, Bartok and Berg, who had embodied Modernism itself in that fissiparous decade leading up to 1914. Not least, any comparison between the 1920s and now has to acknowledge the vastly more extensive contribution the earlier period made to the musical repertoire than our own seems likely to - even if Simon Rattle and his colleagues have stuck mostly to safe choices in some less- than-meaningful juxtapositions for the third instalment of Towards the Millennium.
It is difficult, for instance, to see much point in shoving Sibelius's Olympian Seventh Symphony between Bartok's mechanistic ballet, The Miraculous Mandarin, and Szymanowski's hieratic Stabat Mater in next Wednesday's opening concert - unless, just possibly, that is the point. On the face of it, the sheer variety of trends in the 1920s was more bemusing than ever before. It was a period at once Modernist and anti-Modernist: when the old Expressionist angst contended with the brisk New Objectivity; when a field-based folklorism vied with an industrially inspired constructivism; when the 12-tone row and the 12-bar blues could equally serve as compositional sources; and in the midst of which such masters as Janacek, Richard Strauss, Sibelius, Rachmaninov and Franz Schmidt continued on their own paths regardless.
Yet behind all this proliferating creative activity, it is possible to divine a deep anxiety which, from more recent developments, we might recognise as quintessentially Post-Modern: a sense that the Modernist explosion of circa 1910 had shattered an older, more coherent musical world; and that if the fragments of that coherence were to be shored up again, it could only be through playing down the primacy of originality which had led to the explosion in the first place. One can detect this even in the cult of the lightweight, the popular, the amusing which is most readily associated with the 1920s.
When Jean Cocteau enjoined the young French composers of Les Six - and he might equally have been addressing young Hindemith in Germany, Walton in England or Copland over from the USA - to cast off the old glooms of Wagner and Debussy and cleave to the healthy joys of everyday music, popular song and jazz, he was calling for something the earlier culture would have taken for granted. Brahms felt no inhibition in loving Johann Strauss; Elgar's light music was a simpler cut off the same roll as his concert work. But by the 1920s, only a talent such as Gershwin, coming from the popular side itself, could work up such materials naturally. Even in the apparently naive context of Poulenc, popular borrowings acquire a distinct irony. The little march variation in Stravinsky's Octet (1923), or Schoenberg's 12-tone piano waltz of the same year, sound positively Cubist in their dislocations, and by the end of the decade, Weill was turning such alienated cliches to socially critical use in collaboration with Brecht. Mutatis mutandis, the attempt of such composers as Bartok and Vaughan Williams to evolve a new language out of the age-old vernacular of folk music could never, for all the commanding intellect of the one or the depth of character of the other, quite exorcise a sense of loss.
But the most notorious instance of revisionism in the 1920s was the attempt to re-animate principles of balance and order from the 18th and early 19th centuries: the so-called Neo-Classicism which, in the cases of Stravinsky and Schoenberg, at least, was unjustly attacked as mere time-travelling or academicism. Actually, the 12-tone method, usually construed as the most radical development of the decade, was itself conceived as a classicising device. Having submitted to the nightmare of totally free expression with Erwartung back in 1909, Schoenberg had been searching ever since for a principle of construction that would enable him somehow to feel he was writing string quartets in the great Austro-German tradition once more.
It is at this point that one begins to wonder whether the period actually originated anything except a fascinatingly fragmented new cultural sensibility. Even the deliberate revolutionary percussion-based processes of the early Soviet 'iron foundry' style proved crude echoes of Stravinsky's Rite of Spring, while Edgard Varese's infinitely more significant New York montages, such as Ameriques and Integrales, not only drew many details from pre-war Debussy, Schoenberg and Stravinsky, but their entire aesthetic from the Italian Futurists' manifesto on The Art of Noises published in 1913.
Looking back at the madly eclectic 1920s from the 1930s, Constant Lambert thought he already discerned an art in decline. What strikes us today is rather the crackling vitality of a decade shaken up by a recent cataclysm - the reverberations of which have been dying ever since. For with such symptoms as the neo-Mahlerian symphonies of Shostakovich, or Britten's neo-Verdian Peter Grimes, it could be argued that music itself settled into an ever more feebly circulating neo-history: that the neo-romanticism of the 1930s and 1940s duly divulged a neo-modernist semi-explosion in the 1950s and 1960s, yielding to our more recent neo-post-modern limbo.
Is this why all but the very best today tends to sound not just second but third- hand - yet without recapturing any of the old substance? Under the pretext of smartness or fun, the 1920s may have thrown up some pretty trashy music, but the sheer banal ineptitude of Philip Glass's new 'Low' Symphony, which is doubtless about to roll over the charts in the wake of the inescapable Gorecki, would scarcely have been tolerated. Of course, as many post-1920 composers have demonstrated, gifted individuals can sometimes turn a trick on history - and history may be about to turn some pretty cataclysmic tricks itself. Meanwhile, the magpie choice of the up-coming Millennium concerts at least refutes the old myth of the 'twaddling '20s' by reaffirming something of the richness that once was.
'Towards the Millennium' starts Wednesday in Symphony Hall, Birmingham (021-212 3333), and on Radio 3. A Radio 3 '20s Season' begins tonight