Released at a time when experimental composer Earle Brown was curating A&R for Mainstream (the label also released seminal albums of music by Morton Feldman, Sylvano Bussotti, Luciano Berio and Charles Ives), this album presents two highly contrasting approaches to indeterminacy in musical composition. To perform John Cage's "Cartridge Music" musicians make their own parts by superimposing provided materials (mostly printed on transparent plastic) to create a "complex of points, circles, and biomorphic shapes" which are then used as a graphic score to perform ("generally by percussive or fricative means") objects inserted into phonograph cartridges. Cage's objective was to bring about a situation "in which any determinations made by the performer would not necessarily be realizable." (For example, one player's interpretation of the score might involve turning down the volume of the other's equipment, thereby rendering his action inaudible.) "In this instance," Cage writes, "performance is made indeterminate of itself." Following suggestions from Cage's fellow performer David Tudor, this first recording of the work superimposed four versions of the piece, and despite the fact that contact mics and phonograph pick-ups are now used as instruments in their own right by experimental musicians the world over, this version has lost none of its extraordinary shock value. In stark contrast, side two documents the exquisite pointillism of Christian Wolff's early-'60s music, of which the composer notes that no two performances can ever be the same, thanks to "the way the instruments coordinate and the fact that players constantly have options of what to play." The interpretations by pianist Tudor, violinist Ken Kobayashi ("Duo for Violinist and Pianist"), horn player Howard Hillyer ("Duet II for Horn and Piano") and the string quartet ("Summer") are exemplary, imparting a sense of classical poise and elegant detachment to this austere but deeply human music.