"'Flow of shadows' is how I would translate the composite neolog title of this 1997 work for Orchestra Carbon and how I might describe the musical gestures therein. In seven sections, 'Rheo~Umbra' layers through composed materials, algorithmic strategies for the ensemble, and improvisations by various soloists. The algorithmic approaches include the 'transient additive pulse' where a percussive hit and its reverberations morph into a pulsing groove. There are also hockets and phased looping/transformation of the composed material designed to gradually translate the horizontal -- notes and lines -- into vertical simultaneities. The overall sound design of the composition is an important structural element with the two keyboardists playing samples constructed by me and derived from my own extended techniques on soprano saxophone and bass clarinet as well as an array of sounds produced on the slabs, sounds then layered with their 'live' manifestations." --Elliott Sharp