Classical Music / Philharmonia Emerson Quartet South Bank Centre, London

Saturday's Royal Festival Hall concert by the Philharmonia confounded expectattions. We'd been promised Beethoven, Schumann and Brahms, which is what we got - except that Gidon Kremer smuggled Ferrucio Busoni into the first movement of Brahms's Violin Concerto.

Busoni's cadenza keeps the orchestra involved: first the timpanist has his say, then a choir of strings forges a weirdly modulating route back to the main argument. Kremer himself suggests a Paganini look-alike, bending the knee or balancing on tiptoe, tearing stray hairs from his bow and weaving a wiry thread of tone to maximum expressive effect. His was a hugely involving performance, distinguished by ruthless energy, lacerating chords, filigree passage-work, a deeply dialogic slow movement (the oboist was superb) and a top-speed, gypsy-style finale.

Christoph von Dohnanyi directed a notably well-shaped account of the score, far tougher than his Brahms on record, just as his Schumann Second quite upstaged its CD prototype - certainly in terms of spontaneity. OK, perhaps the first movement's Allegro was just a tad too brisk for non troppo, and the Scherzo's first trio slowed down rather too willingly, but with quick-fire execution, shrewdly shaped transitions, a mellifluous Adagio espressivo and a bracing finale, no one could have missed the point.

Which is more than I can say for Mahler's string-orchestra version of Beethoven's "Serioso" Quartet - the "point" being to shift the balance of power from the private parlour to the public hall. Somehow it all rather misfired: string lines seemed oddly generalised, the first movement gained too much weight, the third lost its abrupt "edge" and the finale's throw- away coda sounded more like busy Mendelssohn than off-the-wall Beethoven. Best was the slow movement, where Beethoven's melancholy drift anticipates Mahler's own, but elsewhere "Serioso" became "Serenade" and the beast was brought unwillingly to heel.

Still, balance was restored at the Queen Elizabeth Hall on Tuesday when the Emerson String Quartet sent shock waves through Beethoven's original, charging the opening Allegro con brio with immense vitality and tossing the final flourish with madcap enthusiasm. It was an exhilarating performance, immaculate, sweet-toned and with much eloquent voicing in the central Allegretto.

The "Harp" Quartet was scarcely less impressive, especially towards the end of the first movement, where the lead violin (Eugene Drucker) provides a wildly arpeggiated accompaniment for some ecstatic dialogue between second violin and viola. The Presto saw cellist David Finckel risking a top-speed trio; but best of all were the first two movements of the big, "late" E flat Quartet, Op 127 - broad, flexible and especially touching in the long theme-and-variations Adagio. The Scherzo was perhaps just a mite formal but the finale protested the full measure of its joyful fury. And what a remarkable movement it is, momentarily reminiscent of the "Ode to Joy" (just two opus numbers away) and crowned by one of the strangest codas imaginable - eerie, unpredictable music with a firm footing in the future.

ROBERT COWAN