Philip Glass, Ensemble: Orion, Barbican, London

An irony of timing brought Philip Glass's latest epic to the Barbican Hall while his former collaborator Robert Wilson's show, The Black Rider, was on at the theatre next door. It was their Einstein on the Beach, that put both artists into the world spotlight three decades ago. As their careers diverged, both have stayed true to a multi-artform ideal of theatre, though on this occasion, the Glass work didn't aspire to spectacle beyond the comings and goings of musicians from five continents.

Orion was commissioned by the Athens 2004 Cultural Olympiad, and it made its London stopover fresh from the premiere in the Greek capital. The binding idea was a myth shared by many countries and a constellation visible from all of them, though the music it inspired was abstract, not pictorial. It was more a tour of Glass's international collaborators - only a couple hadn't worked with him before - and brought to the fore a strand in his voluminous output that has seemed subsidiary, though consistent, from the start.

This time, the Philip Glass Ensemble played host while seven sets of guests, sometimes overlapping, took turns to join it for 15 minutes. With added percussion, the ensemble put a fresh slant on the familiar sound of intimately mixed voice, high woodwind and pulsing keyboards.

Some encounters worked better than others. Mark Atkins' didgeridoo became a thunderous bass to a classic, pulsating Glass build-up, rapid surfaces subsumed in an ascent to grandeur. Foday Musa Suso's kora inspired Glass to respond by reaching further into the African's language than usual. For a set of Scots-derived Cape Breton music by Ashley MacIsaac, Glass simply produced a piano accompaniment as the kilted fiddler stamped and even danced as he played.

Least effective was the Indian episode, not through any lack of brilliance in Gaurav Mazumdar's sitar playing but because the two styles never gelled. Ravi Shankar shared the composing credits, but it didn't sound as though his contribution extended far beyond coaching the soloist. Wu Man, playing pipa, and the Brazilian trio Uakti provided extra instrumental colour in brisk, punchy music that was more Glass than anybody else.

But there was a quietly joyous character to the evening, which came to a head in the seventh piece. Eleftheria Arvanitaki sang a haunting Greek song and, one by one, the others joined in, turning it into a rousing anthem. Even if the Games no longer fully embody Olympic ideals, Orion found them in music.