Two years ago, Oliver Knussen devoted one of his concerts with the London Sinfonietta to the music of Niccolò Castiglioni, the Italian composer half a generation younger than Berio and Nono, whose beautifully chiselled works tend to be overshadowed by those of his great contemporaries. Today, that passing interest could be turning into a bit of a crusade, for Knussen devoted his latest Sinfonietta appearance to Castiglioni again, with six more pieces, and just Julian Anderson's The Comedy of Change, the wonderfully fluent, lithely inventive score he wrote last year for a Rambert dance piece, providing contrast.

Not that Castiglioni's music is in much need of contrast, for its quickness of mind and fabulously assured soundworld provide their own variety, as well as a constant sense of expectation. You never know what is going to turn up next: an exercise in Webernian pointillism can suddenly produce a sequence of diatonic chords or a perky little tune of ineffable silliness; a fractured vocal line will morph into something that would hardly be out of place in a Rossini aria.

Three of the pieces here were vocal, sung by Anu Komsi with confident expressiveness. The most striking was Così Parlò Baldassare, a solo tour de force that is virtually a compendium of 300 years of vocal techniques; the most mysterious an early Elegia, composed in memory of Anne Frank, which atomises its text (anonymous apparently, though the name of the author might have been another omission from the sloppily assembled programme) and embeds it in etiolated instrumental details. The ensemble pieces ranged from the aphoristic 1991 Capriccio, with its larger-than-life solo piano part, to the substantial Quickly of 1994, a sequence of 23 quirky variations, wonderfully lucid and scored, with sparkling crispness and wit.