London Sinfonietta/Brabbins, Queen Elizabeth Hall, London

If the first half of Wolfgang Rihm's Sphäre um Sphäre hadn't so cleverly screwed up the tension from its gropingly uncertain beginnings, I'd have spent far too much of the performance of this piece pondering just what an odd programme it was bringing to an end. And also concluding that, pure practicalities aside, just about any ordering of the five works in this concert would have been preferable to the one actually chosen.

First up had been Jonathan Harvey's new Two Interludes for an Opera. The opera is for Netherlands Opera in 2007, and based on a Buddhist extrapolation around the moment of Wagner's death. These two substantial interludes are scored for 22 players who are subject to some apparently complex spatialisation. I didn't register this as especially remarkable, but it adds another layer to Harvey's rich timbral mix to help create some extremely beautiful sounds and a compelling dramatic context that bodes well for the opera to come.

The first interlude represents Wagner's heart attack, and "the journey Wagner's mind takes immediately after", with a Big Bang of impressive impact followed by waves of alternately slow and faster music, within which Harvey's many imaginative gestures - the repeating strikes and resonances of a gong, the many sudden surges and falls - are vividly shaped. The second interlude, drawing on Buddhist legend, evokes burgeoning young love in a weirdly beautiful cello solo, accompanied by a whole host of wonderful things.

Martyn Brabbins conducted what seemed a fine world première account of these two pieces, and the London Sinfonietta played everything on the programme with loving attention to detail. But as a total experience, the concert was, as I've suggested, unsatisfying.

Following the Harvey, we had the Austrian composer Georg Friedrich Haas's Monodie: similarly slow and sonically probing, but rather blunt and protracted, and for a while bizarrely Wagnerian, in the way it goes about its business. After this, quite a few of the band presumably went home.

James Clarke is a fine but neglected English composer in his forties, but it was a shame that Concetto Spaziale (per Lucio Fontana) was selected as the first piece of his that the Sinfonietta has ever played, since this work for four players and electronics lays down yet another ethereal backdrop but offers only undercharacterised music around it.

Harvey's classic tape piece, Mortuos Plango, Vivos Voco, weaved its usual magic after the interval. But the aforementioned Rihm never delivered the truly epic climax that its first half seemed so firmly to promise. Instead, it frittered its second half away in increasingly sagging attempts to revive the tension and some very empty rhetoric.