MUSIC / Running scared: Robert Maycock on an all-20th-century Prom, including a UK premiere by Alexander Goehr

It was only towards the end of the first half that the initially quiet mood of Tuesday's Prom began to make sense. Quiet in terms of dynamics, that is, not low-keyed in music-making. From the moment that Oliver Knussen let the BBC Symphony Orchestra's flautist start the Debussy Prelude a l'Apres-midi d'un faune quite unhindered, picking up the beat only when other instruments needed a cue, this was a striking fusion of playing that lived and breathed with super-aware conducting - the orchestra's performance drawn out, not an outsider's view imposed. Yet, following as it did the understated charms of Stravinsky's Ode, it gave the concert an awful lot of prelude. There had better be something big coming up.

Well, there certainly was, in its way. Colossos or Panic, receiving its UK premiere, is one of a series of works in which Alexander Goehr has explored large orchestral forms from different angles. If his Symphony with Chaconne had an after-Brahms viewpoint, this latest is like a symphonic poem (it is inspired by a Goya picture) descended from the Franco-Russian line. After its abrasive shock start, it makes the orchestra glitter and beguile. French-sounding sequences and repetitions coexist with a Stravinskian coolness. It is worked out with typical intricacy, but the material is friendly and the audience seemed to be following avidly: none of that all-at-sea restlessness that can pervade the hall in, say, a Maxwell Davies symphony.

Yet it doesn't deliver the pay-off it promises. Goehr is only acting in character when he shies away from crude or obvious statements, but from the way it builds in its later stages you are entitled to expect some decisive moment of truth. Instead, as so often, it feels provisional. One more heave, and it'll be there. The next piece will be really something . . . except that, by then, Goehr's questing intelligence will be on to a different tack.

At some point, composers have to get up on their soap-box and say what they mean. Here even the title refused to choose between Goya's two alternatives, let alone hint at the expressive urgency of a piece that had to be written, rather than an absorbing exercise. Stravinsky, the great coverer-up, eventually let the mask slip with his Symphony in Three Movements, as the concert went on to show. Goehr, the best equipped of senior British composers to make the great definitive statement, still hasn't.

Knussen as composer has a related problem. He recalls the remark that Berlioz is said to have made about an equally brilliant mind, Saint-Saens: 'He knows everything, but lacks inexperience.' If you can do it all, which way do you choose? There's no lack of communicated feeling in his Whitman Settings, eloquently sung here by Lucy Shelton, but the personal voice is harder to pin down. Watching him conduct the Stravinsky Symphony, fast and furious in the outer movements, quick and light (and thriving on it) in the middle, you could see why. As with the Debussy, he was caught up in every twist and turn, living the rhythms as if they were his own. When you care quite so much for other people's music, you have to be ruthless to find room for your own.