Classical: ALLEGRI QUARTET Wigmore Hall, London

Monday's Wigmore Hall Schubert recital by the Allegri String Quartet was something of a musical sauna, with prog:rammes fanning everywhere and a loud volley of cheers when, half-way through the E flat Quartet, all four players abandoned their jackets and ties. The airless environment and high humidity level can't have helped the instruments either: there was much inter-movement tuning and, although the players coped extraordinarily well, their pooled tone tended to stray off the note.

Worst hit was the busy (and comparatively early) E flat Quartet D87: the first movement, while vigorously driven, was conspicuously off colour, although the gnomic Scherzo had a ruggedly Beethovenian profile and the finale harboured some songful phrasing, especially from the leader, Peter Carter. With new recruit Jonathan Barritt a particularly sensitive violist, the current Allegri rather resembles the latter-day Budapest Quartet, in that poetry and "spirit" are invariably placed before polish.

And when it came to the shimmering Quartettsatz, the Allegri's forceful attack was leavened by considerable flexibility. The real point of interest here, though, was Brian Newbould's performing version of the quartet's unfinished second movement Andante, which bravely takes up the argument where Schubert left off (after 37 bars).

Could I honestly spot the join? I'm not sure that I could. Perhaps Newbould's eventful development is slightly over-worked (one passage edges towards Tchaikovskian rhetoric), but as posthumous collaborations go, this is so urgent, sincere and thoughtful that I can't imagine anyone not responding to it. Certainly this audience did.

Come the interval, and virtually the entire house made a frantic dash for the "fresh" air of Wigmore Street. Then came a compelling account of the great C major two-cello Quintet, a big, symphonically conceived affair, with Michael Evans a sympathetic second cellist. And I'm sure I wasn't the only listener who breathed a sigh of relief when the first movement exposition failed to repeat: given the heat and humidity, could we have lasted the course?

Performance-wise, the first movement seemed well "worn in", a leisurely yet capricious account, pliant in its phrasing and full of tiny (though meaningful) expressive hesitations. The Adagio suggested a Brucknerian sense of spaciousness (the initial tempo daringly slow), although the agitated central section was properly vehement. Best of all was the serene mirror-image of the movement's first section, where hymn-like chords were eloquently embellished by the leader and guest cellist - a supremely touching moment. Yet both the Scherzo and Finale steadfastly refused to abandon the darker, more mysterious aspects of Schubert's sublime score. Still, the Finale in particular donned a Viennese-style lilt and the main body of the Scherzo had plenty of bucolic energy. True, there were some rough edges, but the feel of the performance was precisely right, with some especially enthusiastic passage-work from the two cellists. The response was warm, grateful and considerately brief.