The weekend's most astounding noise? Perhaps the historic Gürzenich-Orchester Köln, stretching into eternity with the disparate sound collisions of Stockhausen's Punkte, only to rally into sustained chords that actually echoed a conventional ending? Or the National Youth Orchestra of Great Britain, not one of them over 19, hurling siren, lion's roar, brass battalions, five harps and the kitchen sink into the sonic skyscrapers of Edgard Varèse's Amériques?

Both concerts sent the listener voyaging across time and space and gave the mind much to chew on. Ringing the Stockhausen with two intervals lessened the shock of jamming him into a programme based on the orchestra's premiere of Mahler's Fifth Symphony in 1904. But nothing shrank the players' virtuosity, nor the steely flair of the conductor Markus Stenz. Listening to Punkte, you could be justified in feeling irritated and disorientated. Yet never bored, surely. Drunken lurchings from the brass, scatter- brained string pizzicatos and trills, greased- lightning glissandi, mysterious globules appearing and vanishing: here was music as curious and other as the surface of Mars.

Mahler's great symphony came with its own veil of strangeness. The burnished timbre of the Gürzenich brass played a part; so did the orchestra's relatively modest numbers. Tiptoe endings faded with particular finesse; Stenz's control of dynamics was always effective. Viewed from the other end of the telescope we sometimes missed heft and gusto, in the scherzo most of all. A mixed blessing, all told.

Further little disappointments arrived with the Schubert songs, featuring Angelika Kirschlager and Apollo Voices, backed by new orchestral finery. The two German arrangers, Detlev Glanert and Manfred Trojahn, trotted in dappled colours alongside Schubert's melodies: timid. But Colin and David Matthews gave the exercise some purpose. David led Leise flehen meine Lieder towards the future with a compelling chromatic coda. Colin, more imaginative still, recast the piano part of Nacht und Träume as a luscious night- scape. Kirschlager sang dutifully, no more.

Nothing in the NYO's concert with Antonio Pappano - an inspired choice of conductor for the young - topped the mounting tension and bedlam of Amériques. Rachmaninov's brittle and ruminant Piano Concerto No 4, a gloomier emigré response to America, needed a soloist less off-hand than Boris Berezovsky. Even when the music finally roused itself to the lyric touch, Berezovsky stayed disengaged. The focus sharpened for Copland's Third Symphony: a well-chiselled performance on the whole, though I'd rather live in Varèse's cacophonous America than Copland's flag-waving continent.

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