The vogue for the so-called "Mozart edition" of Handel's Messiah is puzzling. This is the second year that the Barbican's pre-Christmas performance has been presented in the version Mozart prepared for a 1789 revival in Vienna at the behest of a Dutch diplomat who had heard the original years earlier. The alterations are drastic, including cuts and arias redistributed to different voice types.

Its admirers have always argued that Handel, who re-worked Messiah himself, would have used Mozart's larger orchestral forces had they been available. None of Handel's own revisions, however, alter the work's tone as Mozart's do. The differences are clear.

The baleful presence of trombones in the opening Sinfonia pulls us away from religious certainty towards the murkier metaphysics of Don Giovanni. Thereafter, Handel's musical and spiritual purpose is blunted. Mozart invests the choruses with the secular grandeur of their counterparts in La Clemenza di Tito. Handel uses brass and woodwind tellingly at moments of climactic glory. Mozart deploys both throughout, robbing the score of its clarity and power.

The performance, with Harry Christophers conducting the City of London Sinfonia, was impressive. Christophers anchored it in the central meditation on the Crucifixion and Resurrection. The playing was sumptuous and the choral singing, from Christophers' own choir, The Sixteen, beautiful. The soloists were variable, with counter-tenor Robin Blaze too cool in his contemplation of Christ's Passion and bass Michael George making heavy weather of the coloratura. Elizabeth Cragg was the clear-toned soprano, though the real star was tenor Tom Randle, wonderfully alert to every shade of meaning in text and music, and flinging out Mozart's vilely difficult reworking of Rejoice Greatly with glorious ease.