Sinfonia 21 St John's London Sinfonietta QEH

CLASSICAL

"Singing the Century" is a mini-series of three concerts at St John's Smith Square within "Sounding the Century", BBC Radio 3's festival of 20th-century music extending to the millennium. In the first concert last Monday, Susan Sharpe asked George Benjamin, the festival's artistic consultant, if Szymanowski's Songs of a fairy-tale princess were decadent. There was an interesting silence before he answered: "Perhaps." He might have thought to point out that decay brought rich fermentation, and why did Szymanowski's perfectly exquisite score need to be defined by the possible influences on it? That was a more pertinent consideration in the case of Claude Vivier's Lonely Child (1981), since the Canadian composer reacted against his avant-garde formation with an incantatory style dressed in weird but pleasing microtonal chords that evoked a newly invented exoticism.

Varese's Octandre opened Friday's Queen Elizabeth Hall concert in "Sounding the Century", George Benjamin conducting the London Sinfonietta. Three more of Stravinsky's essays in popular or jazz styles, Tango, Preludium and the Ebony Concerto, made for a piquant first half. But the main attraction was Boulez's ...explosante-fixe..., advertised as the London premiere of a version revised in 1991-1993. Like several other of Boulez's composing projects, it's a work in progress and, perhaps, by implication, unendable. ...explosante-fixe... first saw the light of day in 1971 as a memorial to Stravinsky, when it took the form of sketches - a basic musical formula, called "Originel", and seven elaborations, called "Transitoires". What we heard on Friday, at the other end of the composer's intervening thought processes, were two "Transitoires", each roughly 15 minutes, followed by "Originel", about six minutes, linked by two very brief electronic sections, when the lights dramatically went down. Scored for eight strings (stage right), seven brass and seven woodwind (stage left) with three solo flutes in front of them, the music confirmed Boulez's growing concern with proliferating arabesque and recognisable patterning.

The first "Transitoire" was breathless and shimmering. The second began more broadly flowing, admitted more varied gestures and a sense of relaxation. "Originel", giving one solo flute (Sophie Cherrier, very cool and collected) the limelight, wafted and settled. The electronic elements, which also briefly penetrated the instrumental sections, matched, extended and transformed their sonorities into chiming bells. It was the instrumental writing which dazzled with its seemingly casual and unexpected rhythms and harmonies, elegant and effortless.

Boulez says he doesn't like to predict the end of a piece, and clearly he doesn't mean this - or, perhaps, these - to be heard in one particular order. Yet a sense of organic growth, or consequence, was perceptible - with so much none-literal imitation among the instruments and electronics, it felt as if one thing suggested another. ...explosante-fixe... is very cool, and though Boulez mentions the influence of Symphonies of Wind Instruments, his taste for sounds that are sensuous, and the improvisatory, freely associative effect of the music, bring him closer to Debussy than to Stravinsky.