Einstein on the Beach, Barbican Theatre, London

Philip Glass's gargantuan minimalist classic Einstein on the Beach – though he hates the term 'minimalist' – premiered in Avignon, and has taken 36 years to reach the London stage.

It immediately acquired mythic status, with its mode of gestation widely copied by conceptual artists; joint brain-child of Glass and director Robert Wilson, it began as a series of drawings by Wilson – a train scene, a courtroom, some dances, some archetypal images of Einstein - to which Glass matched his score. The playlets interspersing the operatic acts consist largely of poems by the autistic Christopher Knowles, whose lines have a formal patterning. The part of Einstein is played by a violinist, while some of the performers are both singers and dancers, with choreography by the celebrated Lucinda Childs. Glass describes the work as ‘a non-narrative, artificial theatre in which the function of narrative has shifted completely from telling a story to experiencing a story’.

If that sounds gnomic, so is the result. But the lighting is so exquisite, and the music so seductive, that one doesn't bother about the inaudibility of the rapidly-gabbled words. We were invited to come and go at will during this five-hour work, but it was well over an hour before people started scrambling over legs for a break, and they all came back for more. The 'events' in Glass's intricately-patterned score unfold at a glacial pace, and so do Wilson’s images, but their needle-sharp super-reality is mesmerising - or was until the first technical glitch, when a gantry on which a small boy had been standing with a glowing white cube in his hand obstinately refused to be flown out of sight. More glitches followed: Wilson came on to apologise for the fact that we wouldn't get the full effect tonight.

Sometimes the dance is serenely classical, at others it evokes a collision between Modern Times and the 'Ministry for Silly Walks'; the chorus brilliantly manages Glass's softly-pulsating close-harmony effects. The Einstein fiddler’s endless riffs – and answering ones from a solo saxophonist and mezzo – have epic sweep; the nuclear message is gracefully understated; and when we briefly get Einstein alone on his beach, the effect is breathtaking. If you’re looking for 'meaning', this is a monumentally boring show. But if you just say yes, it’s intermittently glorious.