Luigi Nono’s magnum opus, Prometeo (1984), has at last reached the UK, with two sell-out performances in the Southbank Centre’s Fragments of Venice festival devoted to the late Italian avant-garde pioneer.

What is Prometeo? It is a spatial drama which is all over the place, coming at you from in front, behind, above, below, as if the walls of the prosaic Festival Hall have reformed themselves into a house of sound, shifting in space.

Fragments of text, ecstatically high voices in broken chant, volleys of fortissimo brass, a growling euphonium, together with bizarre electronic gurgles, cheeps and barks issue forth without pause for two and half hours. The elusive narrative of the nine movements is almost beside the point: Nono demands only that you listen to this exquisite earplay.

The virtuoso forces of the London Sinfonietta, the Royal Academy of Music Manson Ensemble, Synergy Vocals, two narrators and a cluster of acoustics experts were conducted, in partnership with Patrick Bailey, by the heroic Diego Masson.

Better than any illegal substance, Prometeo sends you into a waking trance, though the sound of dropped programmes suggested the experience induced sleep in others. Only a few sceptics walked out, thinking no doubt that the naked emperor of Modernism was back in town. I’m still in two minds but this was an unmissable event, brilliantly brought off.