Completed in 1994, Ligeti's Viola Sonata is perhaps the least often heard and least considered of his late works. Yet as Geneviève Strosser shows, it is a very considerable addition to the solo-viola repertory. Its six-movement form, beginning with a slow meditation played entirely on the instrument's lowest string and ending with a highly wrought chaconne, shows its debt to Bach's solo-violin sonatas, yet reveals all the familiar harmonic and rhythmic preoccupations of Ligeti's later music. Strosser frames the sonata with the manic moto perpetuo of Holliger's Trema and with Franco Donatoni's explosive Ali, which almost seems about to shake itself apart through its own irascibility; there's Lachenmann's Toccatina, too, a study originally written for violin, and one of Giacinto Scelsi's explorations of microtonal tunings in Manto, which requires the violist to sing as well as play in the final movement. Like every challenge, Strosser takes it totally in her stride.