Oliver Knussen was the curator of Klang, the Southbank Centre's week-long tribute to Karlheinz Stockhausen, and his own contribution to the series was to conduct a concert with the London Sinfonietta, which included Stockhausen's first and last works. The Three Songs for alto and chamber orchestra date from 1951, when the composer was studying with Frank Martin and assimilating a range of 20th-century styles. Helena Rasker delivered them - one with a text by Baudelaire, two by Stockhausen. They evoke everything from Berg to Hindemith, Stravinsky and even big band jazz with a swaggering confidence that must have been startling from a student at the time.

Even more amazingly, the songs link convincingly with music Stockhausen composed more than half a century later. The 10 pieces in Tierkreis, the final orchestral version of melodies composed for musical boxes in the 1970s, have a similarly wide frame of reference, with unpredictable harmonies underpinning melodies following a peculiar logic of their own.

Knussen's concert also included the world premiere of Urantia, the 19th hour from the cycle Klang, in which the recorded voice of a soprano enunciating a mystical text is threaded through a hyperactive electronic soundtrack. The most startling work from Klang had been premiered a few days earlier, when US percussionist Stuart Gerber performed Himmels Tür (Heaven's Door), the fourth hour. It is Stockhausen's realisation of a dream in which he banged on the locked gates of heaven. The player beats on a giant door, until eventually it opens and he passes through. Off stage he begins to play cymbals and gongs, a siren is heard; a young girl walks on, and through the door. It is bewitchingly compelling.