No festival of Harrison Birtwistle's music would be complete without the London Sinfonietta. He has been associated with the orchestra since its beginnings in the late 1960s, and the series of works he has composed for it, from Verses for Ensemble in 1969 to last year's Theseus Game, has provided the connecting thread through his development.

The first of the two appearances by the Sinfonietta in the South Bank's Birtwistle Games mini-festival provided another link with the past. It was conducted by David Atherton, on a rare visit to London; he was one of the founders of the Sinfonietta, and was in charge of several of the early Birtwistle premieres. There were three of those commissions here, interleaved with works by Scelsi - his strange, incantatory Kya, for clarinet (pungently played by Mark van de Wiel) and seven instruments - and Feldman, represented by the second in the Viola in My Life series, as beautifully poetic a piece as anything composed in the 1970s.

Inevitably, though, Birtwistle's music took pride of place, and Atherton drew performances of rare urgency from the Sinfonietta players. Silbury Air (1977) came across as a fascinating study in pulses and the relationships between them, out of which might come eruptive melodic statements or sudden moments of total calm. It's a haunting piece that never quite gives up all the mysteries of its musical complexities.

Secret Theatre (1984) gives a visible form to such relationships, juxtaposing a group of instruments playing melodic ideas with the rest of the ensemble, whose interest is predominantly rhythmic. The line-up of both groups is constantly changing, and so the movements of players between the two provides an extra layer of ceremony - as well as an extra layer to the fabric of a piece that the Sinfonietta delivered with the authority it would give a work by Webern or Varèse.

Birtwistle Games continues until November 11. Box office: 08703 800 400.