MUSIC / Playing musical chairs: Nicholas Williams on Berio at the South Bank

Asked to write an orchestral work, you might begin with the loudest parts, the tuttis, and work out the rest from there. Luciano Berio does much the same thing in Formazioni. Being himself, however, he also rewrites the orchestra. Trumpets, trombones and tubas are placed either side of the stage. Flute and clarinets supplant violins, who are pushed back to where the woodwind should be.

As an image of his mercurial talent to transform and renew the essentials of music, it was an impressive start to 'Berio Renderings', a festival at London's South Bank Centre. Luminous when heard together, Berio's 'formations', or layers of texture, were just as intriguing when teased apart. Hesitant single notes blossomed into rich torrents of sound, with an intensity heightened by the new spatial sense. In the fierce climax, the brass groups hurled volleys of chord-clusters over the heads of their colleagues. Later, a solo flute to the conductor's left wound down the music in duet with a partner hidden in the ranks, until the music stirred again for a vigorous conclusion.

The London Philharmonic under Zoltan Pesko relished both Berio's musicality and their revised seating plan. Restored to standard line-up, they accompanied Yo-Yo Ma's intimate reading of Haydn's Cello Concerto in D with a warm musicianship. Beethoven's Pastoral Symphony concluded the evening with a restrained view of summer.

The Matrix Ensemble's Purcell Room recital explored the relationships of various composers (Berio among them) with the gifted American singer Cathy Berberian. Her voice was there in person in the tape piece Visage, a Sixties montage of superbly executed bangs, clicks and buzzes. In Cage's The Wonderful Widow of 18 Spring, soprano Luisa Castellani perched luxuriously on a grand piano - the only thing to do, it seemed, after the mezzo Mary King's account of the Berio / Weill Ballad of Sexual Obsession.

But even as the focus of the evening shifted from the comic to the serious, one could sense a consistent line of development. In his early James Joyce cycle, Chamber Music, Berio had risked setting one of the songs entirely on a monotone - and had done so with typical panache. The cantata El Mar la Mar explored more alien territory, but its sense of enchantment was shared by Berio's mini-masterpiece, Folk Songs, with the runaway nonsense of its Azerbaijan love song. The conductor Robert Ziegler's own version of Monteverdi's Con che soavita also made a mark, its sounds imagined with a Berio-like refinement and precision.

'Berio Renderings', RFH, SE1 (071 928-8800) until May 14