This ambitious and beautifully produced two-CD set includes nearly all of Iannis Xenakis' chamber music for strings, piano, and strings and piano combined. Chamber music constituted a small part of the composer's output, since large ensembles and large forms were vehicles more commensurate with the aesthetic of his monumental, granitic music. There are no small pieces here, though; in each of these works, ranging from solos to a quintet for piano and strings, Xenakis was able to express his uncompromising vision no less ferociously than in his orchestral works. While all of the pieces have an elemental character, many with a visceral punch, the actual sound of the music is surprisingly varied, and the individual works have distinctive and individual characters. In spite of the weightiness and rigor of the music, the tone is not necessarily heavy, and some pieces, like Evryali for piano and Dikhthas for violin and piano, have moments of what could almost be described as whimsicality.

Violinist Irvine Arditti, pianist Claude Helffer, and the Spectrum ensemble conducted by Guy Protheroe produce consummate performances of the Greek avant-gardist's unwieldy chamber music. If you're familiar with Xenakis's career you'll know he was trained in mathematics and enjoyed a successful career as an architect. Such background might prepare you for the music's preoccupation with line, volume, and form in an unusually abstract way, but it won't prepare you for its visceral, almost primitive power. On Akanthos, the singer Penelope Walmsley-Clark must cope with what is surely one of the most ridiculous soprano parts ever written.