This was one of the earliest exhibitions to be through-designed in the styles of its contents. There was even a "haunted theatre" in which surviving costumes, props, Diaghilev's own walking-stick, floated mysteriously in an atmosphere heavy with his favourite Mitsouko perfume from Guerlain. And - real novelty at the time - in the central hall, dominated by a re- creation of the climactic tableau from The Sleeping Beauty, visitors could listen to a recorded relay of all the major, and many minor, Diaghilev scores in continuous succession.
Admittedly, the 1954 celebration concentrated entirely upon the Ballets Russes years from 1909 to 1929, whereas the Barbican show covers Diaghilev's earlier activities as curator of exhibitions, founder/ editor of the magazine The World of Art and impresario of concerts and operas - stopping short at the outbreak of the First World War, when the Ballets Russes itself had only run six seasons. Nor, after four decades of increasing menace by Muzak, will Barbican visitors necessarily regret that the organisers have refrained from piping Petrushka through the gallery. What is more disappointing - the odd Rite of Spring aside - is the lack of any coherent support for the exhibition in the Centre's concert programmes. After all, those first six seasons alone saw the births of Stravinsky's The Firebird (1910), Petrushka (1911), The Rite of Spring (1913) and The Nightingale (1914), plus Ravel's Daphnis and Chloe (1912) and Debussy's Jeux (1913). And while some of these were heard at the Barbican as recently as Boulez's 70th birthday concerts a year ago, Diaghilev also went on to commission Stravinsky's Pulcinella (1920), Les Noces (1923) and Apollo Musagetes (1928), as well as Satie's Parade (1917), Falla's Three-Cornered Hat (1919) and Poulenc's Les Biches (1924). It is not just that, whatever their varied fates in the theatre, all of them survive strongly in the repertoire, but that several of the Diaghilev ballets could be said to have changed the course of 20th-century music. And the tantalising question is to what extent Diaghilev consciously master-minded these changes through his unique gifts as an impresario.
Music, not art or dance, seems to have been his earliest love, thanks to a cultivated step-mother who sang, and to youthful contacts with both Mussorgsky and Tchaikovsky. Evidently he became a moderately proficient pianist, and when he came up to St Petersburg at 18 to qualify in law, it was really to take singing lessons and to study composition - until Rimsky-Korsakov, no less, flatly told him he lacked talent. At which point, Benois, Bakst and the other young Petersburg aesthetes who had accepted the provincial Diaghilev into their circle watched with awe as he proceeded to transform himself into an expert on the visual arts within a matter of months - revealing for the first time the phenomenal powers of assimilation that were to drive his subsequent career.
Stravinsky, whose brilliant little tone-poem Fireworks first caught Diaghilev's attention in 1908, and who was to remain the greatest of his musical finds, thought that Diaghilev "did not have so much a good musical judgement as an immense flair for recognising the potentiality of success in a piece of music or work of art in general". Indeed, after the riotous premiere of The Rite of Spring, "so far from weeping and reciting Pushkin in the Bois de Boulogne as the legend is, Diaghilev's only comment was: 'Exactly what I wanted.' "
Yet a paradoxical aspect of Diaghilev's feeling for the new was his intuition of just when it might be smart to bring outmoded material back into performance. And once he had settled on ballet as the ideal vehicle for his co-ordinating talents, he duly lavished care upon the revival of Giselle and, most famously, The Sleeping Beauty - that great artistic revelation and financial disaster of 1921. A more ambiguous trend was set in train by the exotic impact of the Bakst-Fokine ballet on Rimsky-Korsakov's symphonic suite Sheherazade in 1910. Up till then, most ballet music had been specially composed, either as part of grand operas by such as Meyerbeer and Verdi, or by commission from major composers like Tchaikovsky or minor specialists such as Minkus. Eventually, over a third of the Diaghilev repertoire was to be based upon pre-existing music, and, if the commissioning of new ballet scores in more recent decades has become the exception rather than the rule, at least among larger companies, then Diaghilev must take part of the posthumous blame.
As for his own new commissions, it is evident that, even here, Diaghilev's motives were often mixed. While he ran real risks by taking up the virtually unknown Stravinsky or promoting an eccentric like Satie, he was on safer ground commissioning such established figures as Debussy and Ravel while, in pursuing the most successful composer of the day to create The Legend of Joseph (1913) for the young Massine, he was plainly dreaming of profits; Richard Strauss was not inspired, however, and the work has been forgotten.
Yet, in the longer term, some of Diaghilev's most integrated triumphs of total theatre were to prove the most vulnerable - or, at any rate, those who thrilled to the original Stravinsky-Benois-Nijinsky Petrushka or the Falla-Picasso-Massine Three-Cornered Hat tended to lament ever after that subsequent stagings never seemed quite the same. Nor were Diaghilev's own collaborative instincts by any means infallible. For several years he tried to persuade the outraged Stravinsky to compose a ballet version of the Russian Orthodox mass under the title Liturgie - though his oddest project was surely the ballet on Cupid and Psyche he tried to commission for Nijinsky in 1913 from the marmoreal stage designer Edward Gordon Craig and our own Ralph Vaughan Williams.
Yet the imposing succession of scores remains - not just the celebrated titles but such varied curiosities as Florent Schmitt's Tragedy of Salome (1913), Prokofiev's Le pas d'acier (1927) or Henri Sauguet's La chatte of the same year, which the Barbican might helpfully have given an airing. So what exactly was Diaghilev's contribution? One could argue that, in creating the special conditions for Daphnis and Chloe or Les Biches, he enabled Ravel and Poulenc, in their different ways, to write on a broader scale than they had before; one might assert that the scenario of Jeux compelled Debussy to fuse his most seductive and innovatory impulses, or that Parade persuaded Satie to cross-cut for the first time his sardonic and hieratic styles. But the test case remains Stravinsky. The pre-Diaghilev works, somewhat stiffly modelled on Tchaikovsky, Glazunov, Rimsky, with just a dash of Scriabin, hardly suggest an innate revolutionary. Indeed, one might doubt how far he might have developed had Diaghilev not brought him to the West and provided the support and excitement which ultimately inspired him to blast his cultural background to blazes in The Rite of Spring. According to his second wife Vera, many of Stravinsky's opinions even in old age were "virtually parroted from Diaghilev". Having fundamentally affected the course of possibly the greatest composer of the 20th century, the creator of the Ballets Russes deserves to be remembered at the very least as a catalyst - of genius.
n 'Diaghilev: Creator of the Ballets Russes' continues at the Barbican Art Gallery, London EC2, to 14 April (0171-638 8891)