MUSIC / Time and motion study: Nicholas Williams on a Sawer premiere at the Proms

EARLIER this year Dominic Muldowney's Violin Concerto showed how several contrasting tempi might be combined simultaneously in a single piece. David Sawer's 1992 Prom commission, Byrnan Wood, performs similar tricks with the spatial element of musical performance. Though the players of the BBC Symphony Orchestra remained stationary on Tuesday evening, the effect of thematic material passing between neighbouring groups or related timbres was intended to project an idea of the ensemble transforming itself from within. The aim of this musical camouflage was that, like Malcolm's army on the march to Dunsinane, the sound of the orchestra should literally appear to move.

In the event it was less the evolving geographical aspect that caught the imagination than the confidence and flair of the developing musical argument. That Byrnan Wood was the composer's first essay in this medium seemed hardly relevant. Sawer, who is 31 this year, was a pupil of the German experimentalist Mauricio Kagel, and has a wealth of experience in music-theatre already to his credit. Handling an ensemble of quadruple wind and five percussionists with delicacy as well as forcefulness, he painted an image of conflict that grew ever more resolute with the ebb and flow of its broad, expressive paragraphs.

Backward glances in the direction of The Rite of Spring, menacing horn calls and a wild, weird shriek from altissimo piccolos were all part of the drama. Particularly memorable was a recurring motif of spectral, flickering strings, weightless at first, then tethered down by brass and gongs echoing across the auditorium as each deep sonority discovered a sympathetic resonance in another instrumental group.

Whether this appeared like an orchestra shifting position partly depended on your location within the rotundity of the Royal Albert Hall. In fact, one had the impression that Sawer composes like this anyway, gestures working their way through the texture by means of musical osmosis. If the metaphorical implications of the title were a little shaky, what remained was a gripping Shakespearian tone poem, and a notable addition to the repertoire of war music, stretching back to Beethoven's famous symphony depicting Wellington's triumph at the battle of Victoria.

Macbeth's tragic destiny seemed all the more violent beside the coolness of Rachmaninov's The Isle of the Dead, which opened Tuesday's Prom. A natural choice for a programme that dwelt on mortality, this represented another genre: Russian water music. It's a category that includes Lyadov's study The Enchanted Lake (also written in 1909) and extends to Stravinskian berceuse movements in The Firebird and The Fairy's Kiss. Mark Wigglesworth conducted this portrait of Charon's voyage across the Styx with care and discretion, while reserving an abundance of energy both for the Sawer and for Shostakovich's Babi Yar symphony after the interval.

No stranger to this composer's late style, Wigglesworth directed the piece in its original version, restoring Yevtushenko's censored verses about Russian anti-Semitism. With the men of the London Philharmonic Choir and Southwark Festival Chorus in excellent form, and John Tomlinson delivering the bass solo in flawless diction, this was a memorable encounter. Old paradoxes about the form - symphony, cantata or suite? - were dissolved in the weight of this reading. The visible audience relief at the arrival of the banal flute waltz piping in the last movoment, 'A Career', was evidence of Shostakovich's power to sustain tension on an epic scale.

Schubert once told a friend that he knew of no happy music. With Babi Yar's warnings of repression and compromise as grimly appropriate as ever, you came away from this concert tending to feel the same way.