Elliott Carter as cheer leader? The 91-year-old composer looked on last Tuesday as his youthful indiscretion enjoyed a rare action replay. His 1944 Holiday Overture was a cheer all right, a last hurrah for the "new deal", the new aesthetic of Aaron Copland, whose "simple gifts" had so eloquently restored pride in America's musical heritage. But, more than that, it was a celebration. Paris, city of Nadia Boulanger, mentor to both composers, had been liberated and Carter was going to kick some ass. Holiday Overture is Walton's Portsmouth Point with rim-shots. Sassy and syncopated. There's a fugue - a mark of respect, perhaps, for Boulanger's quiet classicism - but the pay-off is pure Charles Ives with each of Carter's themes jostling for pride of place in the victory parade. It sounded like something the Dallas Symphony might have left behind, except that Oliver Knussen and the BBC Symphony played it with the kind of muscle and true grit that, dare I say it, was more American than the Americans.

This was a concert about "the special relationship" between them and us. A real hands-across-the-pond affair. Benjamin Britten's Suite on English Folk Tunes, "A Time There Was...", with its strange refractions of a post- Mahlerian sound world, is ultimately retrospective, taking us gently by the hand to that final resting place for the entire English folk tradition. A lament for lost innocence. Meanwhile, across the great divide, across the interval, Ruth Crawford Seeger, Charles Seeger, and Aaron Copland were rediscovering theirs, hitching America's past to its future and railroading the present with feisty arrangements of "songs my forebears taught me". The symmetry was poetic. A difference in attitudes: "lest we forget" versus "like hell we will".

But then, as if to confound our national prejudices altogether, the evening engineered an amazing face-off between two new works. Carter's "Allegro scorrevole", the third and final panel of his orchestral triptych Symphonia, is a winged messenger so refined, so European in its sensibilities that it's almost as if Boulanger has reclaimed Carter for posterity. Mark-Anthony Turnage's Dispelling the Fears, for two trumpets and orchestra, is, on the other hand, an essay so infused with the soul of American jazz blues that its lasting legacy will, for this listener at least, be as a siren song for Miles Davis.

Carter's piece confounds with its sheer airiness, its manual dexterity. The composer is an old man, the composition - to use the vernacular - has just gotten going. Berlioz's "Queen Mab" Scherzo was said to have been the model here, but Carter has taken the sound concept further still. Everything floats, hovers, darts. Woodwinds play at being hummingbirds or fireflies. Heavy brass is weightless and muted, sat watchfully on the columns of air from two rippling vibraphones. The only real moment of tangibility comes with a sudden climax, a fall to earth. But otherwise the spirit (and beyond the music's characteristic abstraction, it moves here with the deftness and agility of a teenager) is buoyant, waiting for that inevitable moment when - like the solo piccolo in the closing minutes of the piece - it will, without fuss or ceremony, simply vanish. Vapourise.

Turnage's piece begins with a pulse. A kind of magnified heartbeat. And almost before you've registered them, two trumpets - the amazing Hakan Hardenberger and John Wallace - are one, spinning off into futuristic baroque-like riffs while cawing soprano saxes - roosting high above the woodwind chorus - imitate and mock. The orchestral colours - and in particular the shadowing of bass and tenor tubas - are astonishingly arresting, and beautiful. The legacy of Britten does indeed live in Turnage. But the heart of this terrific piece - one of Turnage's very finest - is the eternal blues which evolves and re-evolves in a kind of perpetual slow motion. The full-stop at the end of the piece is a sham. Rather like Copland's Billy the Kid at end of the concert. Heroes come and go, but the music goes on.

Edward Seckerson