Provocative pieces from Shai Wosner

The latest theory on why Mozart was his singular self sounds suspiciously facile: Now, according to some medical experts, it seems the great genius was bipolar. Well, who isn't?

Whether or not pianist Shai Wosner subscribes to that idea, he began his concert with the Miro Quartet on Friday with a solo piano work, the Fantasy in C minor, K. 475 - one of the darker, crunchier pieces Mozart wrote - in a performance that went convincingly to more extremes than usual (and not just to block out a noisy hearing aid in the audience). Fine gradations of intensity, touch, and nuance were everywhere in this unusual start to a provocatively unorthodox Philadelphia Chamber Music Society program at the Kimmel Center.

The Fantasy's counterpoint and sense of simultaneous music events were a logical bridge to three Bach pieces adapted by Mozart - unconvincingly - for string trio. Bach's counterpoint was muddied, but its strength of purpose kept Mozart from asserting his own personality. It said much about what Mozart is not. Bach found God in the mechanics of composition. In Mozart's secular world, mechanics were subsumed by a larger personal expression, as in the Fantasy.

All of these elements were heard in happier balance in Mozart's familiar Piano Quartet in E-flat major, K. 493, though the performance didn't let you slip back into mere enjoyment. The normally graceful passage work had Bach-like toughness in Wosner's hands. Parts that usually sigh and swoon instead revealed greater underlying musical integrity. The piece's emotional range wasn't tempered by surface charm. Mozart shouldn't always be played this way, but I'm grateful to have heard this.

Wosner is emerging as an increasingly important artist: His excellent debut disc on the Onyx label juxtaposes piano miniatures by Brahms and Schoenberg - who had far more in common than one would think - though with a yielding performance manner that didn't prepare me for the domineering personality heard Friday in Dvorak's Piano Quartet, Op. 87.

Not the sort of chamber pianist who envelops his collaborators with warm sonority, Wosner creates something akin to a magnetic field that draws everybody along with brisk, unsentimental tempos and a manner that, in the Dvorak, had an amplitude one associates more with Rachmaninoff. Sometimes, the music was bullied. Writ larger, the piece reveals the composer's ill-advised decisions to juxtapose palm-court fluffiness to folk-influenced exoticism that sounded almost Middle Eastern. It's good to get a break from the greatest-hits chamber works, but this one perhaps responds better to coaxing rather than to manhandling.