Nash Ensemble/Friend, Purcell Room, London

The Nash Ensemble might be criticised for failing to represent more than a narrow brand of musical modernism but, as the latest concert in its 40th-anniversary series showed, the seam of contemporary music which it taps continues to throw up some very fine music. Efficiently conducted by that Nash stalwart, Lionel Friend, it was superlatively performed, too.

Throw in world premieres from Elliott Carter, Colin Matthews and Harrison Birtwistle, and a pre-concert talk with all three composers, plus Julian Anderson (whose 1997 Nash commission, Poetry Nearing Silence, was also on the bill, together with Oliver Knussen's Ophelia Dances), and you have a scintillating evening. What a shame, then, that this concert, which in Birtwistle's new work featured a London-Sinfonietta-sized ensemble, took place in the cramped Purcell Room.

At 96, Carter still shows no sign of slowing down, and his musical mind seems as sharp as ever. His new piece, Mosaic, helped to give the concert a kind of theme as, like most of the rest of the works on the programme, it is an assembly of fragmented musical moments. Mosaic is the latest of Carter's tributes to friends made during his extraordinary life. Here it was Carlos Salzedo, a harpist from whose book on contemporary harp techniques Carter selected those he liked most to make a miniature, but fiendishly difficult, concerto for harp and seven other instruments.

The result is, perhaps, not Carter at his very best, not least since the focus on extended techniques for the harp, as well as the unusually fragmented approach, undermines the flow of this composer's familiar musical discourse. But there are wonderful things in the piece all the same: from almost every kind of harp-sound and playing style you could imagine to the showcasing of viola and oboe in fine melodic profile amid the accompanying ensemble activity. Lucy Wakeford dispatched the solo part with an aplomb especially commendable in someone playing a new work in public for the first time.

Matthews's A Voice to Wake is a setting for soprano and small ensemble of two poems, here intertwined, by the now-obscure 19th-century Scots poet John Davidson. The piece teems with all this composer's usual instrumental ingenuity, but I couldn't understand why Matthews feels so strongly attracted to poetry of such leaden tread and dubious modern relevance. Claron McFadden did her best with the solo part; with the cellist Paul Watkins she had earlier been riveting in Birtwistle's Nine Settings of Lorine Niedecker, another previous Nash commission.

Birtwistle's new Cantus Iambeus simply bursts with all its composer's usual energy, quirkiness and obsessions. It's a short piece, but its visceral ensemble energy, grinding to a halt sooner than expected, made a fitting conclusion.