by Dan WarburtonFour different versions exist of Alvin Lucier's 1972 work Still and Moving Lines of Silence in Families of Hyperbolas, of which this is the second (the others are gallery installations with or without percussion, and a live version with dancers). It consists of 12 separate pieces for instruments -- 11 solos and one duet -- playing with fixed oscillator tones. In most of the pieces the musicians sound 16 long notes, separated by silences, against one or two fixed oscillator tones, slightly raising and lowering their pitch to produce audible beats of varying speed. Four of the pieces, however, are scored for pitched percussion -- marimba, xylophone, glockenspiel, and vibraphone -- and since these instruments are unable to execute microtonal glissandi, Lucier instead calls for slow accelerandi and ritenuti. The interference patterns and aural byproducts produced -- illusory glissandi, the apparent movement of sound around the listening space -- are extraordinary. The reduced forces and utter simplicity of the concept make Still and Moving Lines an austere but spectacular listening experience. Not for headphones though: the sharp stereo separation of oscillator and instrument is designed to send the waves into the listening space, not the inner ear.