MUSIC / Transformations of a chameleon conductor: The Mozart players' new director can be dashing and dignified. Nicholas Williams observed the mix at the QEH

THERE ARE two sides to Matthias Bamert - rather Jekyll and Hyde. Mr Bamert the earnest, dignified conductor may often be seen directing 20th-century masterpieces and new works with all the authority to be expected from an apprentice of Stokowski and George Szell. The other Mr Bamert seems a quite different manner of man: smiling, ebullient, he throws caution to the wind, conducting classics by heart. Freed from observance of the score, he treats the podium as a dance floor, wielding the baton like a rapier.

Both sides of his personality were on vigorous display at Wednesday's QEH concert by the London Mozart Players, of which he has recently been appointed Musical Director following the departure of Jane Glover. Bamert the man-in-control was evident in the Passacaglia for strings by his Swiss compatriot Frank Martin, a tough, disciplined curtain-raiser. Earlier this century, Martin, with typical native diplomacy, bridged the gap between atonality and tonality by crafting Teutonic, quasi-serial pieces spiked with an intriguing dash of Gallic charm and elegance. The Passacaglia accomplishes this aim with conviction and flair, a 15-minute study of changing backgrounds against the unbroken repetition of an angular chromatic theme.

Though scarcely melodious in a conventional way, Martin's music has a manner of weaving a compelling contrapuntal fabric whose textural discoveries linger in the memory: viola spotlighted against a haze of three violins; knotted polyphony slowly infiltrated by Bachian flourishes and lapidary dotted rhythms. Bamert caught the essence of its grand gestures, but was mindful of their origin in an equally impressive restraint.

He was also an ideal accompanist in Mozart's E flat major Piano Concerto, K449, Howard Shelley playing an elegant, polished solo part in this most chamber-like of Mozart concertos. Strings were at their best in the slow movement, shaping its square, formal opening into a piece of enchanted night music underpinned by lingering, sustained notes from nocturnal horns. Repeated chords on upper instruments dovetailed to the piano's statements with ease and precision. Elsewhere, lower strings fell foul of their own enthusiasm. The unseemly rasp of double-basses in more vigorous passages only emphasising how this orchestra has always seemed weakest in its middle registers, despite some fine-toned individual playing from violas and cellos.

But all this was redeemed by the arrival, in the second half, of Bamert the showman, conducting Tchaikovsky's Serenade for Strings from memory, and drawing Italianate sunshine from a work which, though its finale includes a Russian folk song, sounds refreshingly free from deep Slavonic anguish. The key to any performance is the 'Elegy'. True, this can be lustrous, generously paced and reverent; but here it was a more amiable musing on things past.

Trumpets, timpani and clarinets augmented the band to full strength for Mozart's Six German Dances, K509, a sparkling medley of interlocking waltzes and trios, with a wildcat piccolo part that went berserk in the final bars. If this kind of programming and conducting is typical of the Bamert regime, then expect a season of music-making which, like the Mozart, is more than the sum of its parts.