Late in his life, New York School composer Morton Feldman was prolific. This piece, written less than a year before his death stands, with "For Philip Guston" and his two string quartets (one of which is six hours long), as a statement on the relationship of music as sound, how they interact with one another and separate into different entities over extended periods of time when notions of rhythm, pitch, timbre, etc., are dispensed with. But Feldman was an exacting composer when it came to dynamics. Basically, there weren't any; all of his late music, of which "For Christian Wolff" (written for another member of Feldman's circle, the composer by the same name) is a prime example. Almost three and a half hours in duration, the work is composed in 12 movements, where one ends and another begins is anybody's guess. The piano and celesta are scored for pppp, and meant to be played back just above the level of silence. This spaciousness and constant but sparse activity is meant to allow for other sounds to enter the composition that would normally be heard. When Feldman would tour with his works, he was very aware -- usually jovially -- at just where an audience member would cough during a performance. Often just one instrument is playing one single note, responded to by the other instrument playing its same note for long periods of time. They gradually evolve into the piano or celesta playing chords in brief clusters while the Flute is playing an almost unheard trill. Eberhard Blum and Nils Vigeland were both supervised by Feldman in the debut performance of this work. They were his students and collaborators who understand implicity the rigors of performing his work, which is, for the listener, almost overwhelming in its ambiguous, haunting beauty. To listen to the entire piece, on a 5 CD changer, is, for the listener, a transformative experience; it's a chance to encounter our own view of sound and its (lack of) varying forms. There is plenty of room for listeners to roam around inside "For Christian Wolff," specifically, because for the performers there is no room for variation from this demanding, unfolding of the score. As is the case with most of Feldman's late work, it can be ignored as background music, or it can be entrancing as a journey into a hidden universe; profound and mystifying.