Aaron Copland is one of the featured composers of this season's Proms, and the London Sinfonietta and Oliver Knussen celebrated his achievement in a late-night concert that focused on rarities from his output, with startling results.

Copland encapsulated the vastness of America and drew on its folk heritage. But we tend to forget that he trained in Paris, and the Prom brought home the realisation of how French some of his music sounds. The opening of his Clarinet Concerto has been compared with Appalachian Spring, but its limpid melody over a deep, pulsing accompaniment disconcertingly recalls Satie's Gymnopedies. Jazz influences enter the piece later as the pace gathers. It's as if the work describes a States-wards journey out of Europe, culminating in the dazzle of New York. It requires a virtuoso soloist and in Michael Collins it finds perhaps its ideal interpreter.

Music For The Theatre was seen as quintessentially American when first performed in 1925, though its tangy sonorities and brassy sleaze conjure up the work of Parisian dives. Stravinsky-style rhythmic propulsion lurks behind the so-called Short Symphony (in reality, the Second) of 1933 - deemed unplayable in its day. Knussen and the Sinfonietta flung it out with buoyancy.

I was less happy with Lukas Foss's Time Cycle. Berlin-born Foss's music was admired by Bernstein in the 60s. Time Cycle, for soprano and orchestra, peers back from America towards Europe. Rosemary Hardy voiced the songs with voluptuous ease, but neither she nor Knussen could quite disguise the derivative quality.