Violist Kim Kashkashian in peak form

The music world is crawling with hot young violists (Maxim Rysanov, Lawrence Power, and David Aaron Carpenter) but they all have a ways to go before they're as interesting as Kim Kashkashian. At age 59, she is playing in peak form, and more than most, expanding the viola repertoire in numerous directions. But rather than probing some meditative new works by Baltic Republic composers or exploring her Armenian roots, Kashkashian played nothing but her own Schumann adaptations Friday at her Philadelphia Chamber Music Society recital.

Why not?

Adagio and Allegro Op. 70, Fünf Stücke im Volkston Op. 102, Fantasiestücke, Op. 73 were refitted with success. Violin Sonata in D minor Op. 121 was not - an enterprise that told you a lot about what was right with the other transcriptions and why such things aren't widely attempted.

Though the sonata was composed in 1851 and only two years after the rest of the works on the program (all were written within weeks of one another in 1849), it is from a different creative period: The composer was knocking out works faster (and perhaps more carelessly) than before, often spending little more than a week on each one, almost as if he knew that, amid encroaching mental illness, his creative days were numbered.

The sonata's third movement is among the composer's most original, with an Italianate melody that's plucked out of the instrument with charmingly rustic effect, in what feels like Schumann's answer to the Act II serenade in Mozart's Don Giovanni. But the final movement shows the composer at his most obsessive, with a five-note motif arriving somewhere about 50 times in less than eight minutes. Much of the rest feels dense to the point of claustrophobia.

Without the brighter sound of the violin, such passages became murkier. Accompanist Robert D. Levin seemed to compensate by bringing a Bachlike sense of definition to the piano part, but the effect felt relentless in stretches where the music so energetically goes nowhere.