LSO / Davis / Lang Lang, Barbican, London <br/>International Mahler Orchestra, St John's, Smith Square, London

Can Lang Lang, the brilliant young Chinese pianist currently promoted as "the hottest artist on the classical-music planet", really play Tippett's Piano Concerto? Is Sir Colin Davis losing faith in a composer who meant so much to him? Such questions were difficult to evade after a concert that, against expectations, proved so curiously unsatisfactory.

Sir Colin set the magical opening of the Concerto going at a surprisingly brisk pace and then seemed to stand back and let it run, setting both pianist and woodwind of the London Symphony Orchestra quite a task not to let the more ornate patches degenerate into a scramble. Indeed, Lang Lang scattered a fair crop of wrong notes and almost came unstuck in the cadenza, while his metallic tone and oddly random left-hand dynamics generated more energy than charm in the finale.

As if by compensation, Sir Colin launched the opening chorus of Tippett's A Child of Our Time at a turgid pace. Elsewhere, tempi were too fast. Of the four soloists, only the fine bass Narrator Matthew Rose got the contained formality right, and while the London Symphony Chorus delivered the double fugue, with which Tippett just contains the violence of Kristallnacht, punchily enough, they sounded less than spot on elsewhere.

The International Mahler Orchestra seems to be a training outfit for young professionals seems, because the programme notes divulged little. And the actual programme was way too long by the time Beethoven's 40-minute String Quintet in C was played, one's ears were satiated. Which was a pity, for there were some promising players, not least the agile oboist Hernando Escobar in Britten's Phantasy Quartet, composed at 18, which opened the evening.

Receiving its UK premiere, String Quartet No 1 (1999) by 35-year old Florian Kovacic was a pleasing postmodern assemblage of jigging cross-rhythms and mildly dissonant harmonies, if somewhat tentatively played. Stronger in effect were the Five Pieces for String Quartet (1923) by Erwin Schulhoff (1894-1923), friend of Berg and victim of Hitler.

But the high point was Ravel's demanding four-movement Sonata for violin and cello (1922): the volatile virtuosity of violinist Tristan Thry answered by the firmness of cellist Kajana Packo. One has rarely heard a reading of more life and sweep. Pianist James Redfern and cellist Yoel Gamzou took their turns after the interval in Mahler's turbidly tragic Piano Quartet in A minor, composed at 16.

And so to Beethoven's only String Quintet, a neglected near-masterpiece. Here, again, the risk-taking spontaneity of Thry's leadership, especially in the scudding finale, rekindled enthusiasm at the end of a long, long evening.