Film music LSO / John Williams Barbican, London

Renewing his fruitful relationship with the LSO, begun in the late Seventies with the recording sessions for Star Wars, John Williams padded on to the podium for Friday's Barbican concert of his film music like a benign schoolmaster. His anti-authoritarian conducting style clearly put the band at its ease: Williams directed fast marches in half-time with one hand in his pocket, and at one point (during the makeweight Cowboys Overture) actually appeared to be riding an imaginary horse. The downside of this relaxedness was that dramatic tutti stabs were never tight enough, and at slower tempi the ensemble became decidedly ragged.

The first item was not film music at all, but the official theme for the Atlanta Olympics, Summon the Heroes. Williams summoned up the usual suspects - brass (clambering as usual up and down the harmonic series) and martial snare - for his grandiloquent opening. But as well as a particularly rich horn-trumpet psychomachia, there were some lovely modal passages for skittering woodwind, and a Copland-esque angular spaciousness throughout. Intelligently rousing stuff.

The rest of the evening - essentially a Greatest Hits compilation - divided into two sorts of piece. Either hearing the music unencumbered by zapping lasers and dialogue is a revelation or (notably in the extracts from JFK) you get the feeling Williams was simply stuffing time with notes. But when it's good, it's terrific. Williams's harmonies are surprisingly adventurous: Princess Leia's theme from Star Wars, for instance, has some astringent whole-tone counterpoint under the naive melody. And he avoids stodginess in the epically noisy sci-fi marches with closely interwoven textures - theme and accompaniment playing exclusively in the syncopated interstices left by one another, teasing, until they coincide at the climax.

As a reprieve from the fortissimo showboating of Star Wars and Superman, an excerpt from Close Encounters of the Third Kind offered some of Williams's most imaginative colourings, with weird tuba glissandi and a twittering piccolo intersecting dissonantly with sighing cello runs, until the film's five-note leitmotif is smuggled in beautifully with a solo oboe over sostenuto violins. Later on, the spare, romantic lines of the Schindler's List theme proved Williams's underexploited talent for sensitive orchestration, but the solo violin played with such terrible, drama-queen vibrato (the antithesis of Itzhak Perlman's restrained performance on the film's soundtrack) that the effect was almost ruined.

After a final burst of ET, came two encores: the first a bluesy theme from Sugarland Express, which unfortunately came down to straight musicians trying to play jazz; the second the irresistible Raiders of the Lost Ark theme - hugely exciting, and utterly shameless when it modulates up a tone for the finale. The LSO shook off its unusual torpor: the horns, which had sounded tired and inaccurate most of the evening, gave their all. A raucously appreciative capacity crowd saved its biggest cheer for last.