MacMillan Premiere Barbican Hall, London
James MacMillan's symphony, Vigil, given its world premiere on Sunday by the LSO under Mstislav Rostropovich, begins with dense shifting clusters in the cellos and double-basses. This Scottish composer long ago hijacked the sliding string sounds familiar from avant-gardists such as Xenakis and Penderecki and turned them to fresh purpose as part of his Celtic keening vocabulary. Clusters, too, are scarcely unknown in his earlier output. But this score's first pages still look dangerously modernist for a composer with MacMillan's popular reputation.

These opening sounds are emblematic of the whole work. Though Easter plainsongs subsequently play a significant role in this final panel of MacMillan's Easter Triduum (written for the LSO), in the wake of The World's Ransoming (for cor anglais) and the Cello Concerto (for Rostropovich), both premiered last year, the new symphony offers textural sounds less often alleviated by the reassuring strains of melody than they have usually been in his output. And though the chant he employs brings with it a permeating modality, triadic harmony is sparingly used. The fragmented and distant nature of the opening clusters perhaps prepares the listener for a work in which discontinuity is, for long stretches, a notable feature.

MacMillan talks of an "opposition between extremes of darkness and light, as well as a continual journey back and forth between these two polarities". The darkness of the first movement (despite being rather perversely called "Light") is an apt beginning, eventually rising from its murky depths with the help of the cor anglais of The World's Ransoming and introducing an off-stage brass quintet before erupting into some light-suggesting Messianic rhythmic unisons.

The second movement, "Tuba insonet salutaris", however, rather rashly maintains the hesitant pace and protracted utterance. The five brass players are ranged around the auditorium to offer the "Exultet" chant from the Easter Vigil, and it's true that this makes them part of a much more active orchestral landscape. But the music generates too little tension to make one feel there's a real progression going on. Was Rostropovich - charismatic but never strong technically - partly to blame? Matters aren't helped by having a tuba next to your right ear, of course, but the whole orchestral conception of this symphony - giant wooden cube and all - is anyway surely better suited to the Albert Hall than to the Barbican.

It's not until "Water", the last and longest of the work's three movements, is well underway - around half an hour into this epic 52-minute celebration of the Easter Vigil - that triadic harmony really kicks in. By then the fierce opening has generated rhythmic unisons which this time offer an appropriate catharsis. The subsequent full-blown chorale, which constitutes part of the work's apotheosis, overlaid by excited paeans in which the violins that have been silent throughout the first two movements take an important role, is, surprisingly, the sort of joyous outburst of energy in which MacMillan excels. In a limited sense it's been earned, too. But it's an awful long time coming.