(1985) Four percussionists and Tape
This piece explores the physical, acoustic possibilities of percussion instruments, especially through rhythm – rhythm as structures in space and time, as cyclic repetition, and as a pattern with a steady beat. The title Of Radiant Streams refers to ‘streaming’ –a perceptual quality of the auditory system in which the breaking apart of individual elements at high-speed creates an experience of hearing several streams.
A repetitive cycle of tones spread over a certain frequency range may be temporally coherent, or integrated, at a particular tempo. It is possible to gradually increase the tempo until certain tones group together into separate streams on the basis of frequency…the faster the tempo, the greater the degree of breakdown or decomposition into narrower streams until ultimately every given frequency might be beating along in its own stream. 
The word stream is also related etymologically to rhythm; both are rooted in the Greek rhein, meaning “to flow”. Another essential element of this piece is room acoustics–I mapped out a general range of resonant frequencies for performance spaces in an effort to have the whole room vibrating sympathetically with intense sound pressure by the end of the piece. I began by establishing a frequency range from the extreme registers of the highest and lowest instruments. The highest instrument was the glockenspiel (4,186 hz) played with brass mallets to maximize the high frequency of the sound. The lowest was the bass drum (50 hz). I then expanded the frequency range by taping and then playing back the original sounds at up to four times the original speed. The taped part in Of Radiant Streams consists of a steady stream of multitracked, acoustic sound with continuous internal timbral modulations.
The form of the piece is based on a Fibonacci spiral–the total duration is 21 min. and the structural points of each recurring cycle occur at 1,2,3,5,8 and 13 min. The piece begins with solo tape–a delicate, sparse texture created with several tracks of antique cymbals (I removed the attack part of the sound, leaving only the resonance). The evolution of density and intensity in the pitched sections were created with fast, repeated note groups that slowly break off into separate streams. Each cycle of the piece consists of an entirely pitched or unpitched section, and the cycles alternate between pitched and unpitched sections.
[This is a Fibonacci spiral, which forms of basis for Of Radiant Streams, with indications for the recurring cycles within the composition.]
At the 8-min point, the second cycle of the pitched section begins. Fast, repeated note groups begin at seven or eight notes per second, with the note groups in each part playing pitches within a close frequency range, and all within the frequency span of an octave. As the instruments play note groups of varying speed within the same frequency range, a series of interference patterns is produced, which creates the perception of a large, two-dimensional (2D) field. The note groups slowly expand into a wider range and reach maximum density, intensity and volume at the 12-min point. The combination of note groups and timbres then create interference patterns with maximum intensity and the fast, repeated note groups blur into frequency ranges; the frequency ranges begin to separate into streams. Once the frequency ranges break down into separate streams, there is a complete loss of a sense of structured time; each of the percussionists plays note groups as quickly as possible while creating a large, 2D sound field where individual elements cannot be isolated. The music moves out of a linear sense of time progression and into a large sound field, or texture.
 Albert Bregman and Stephen Mc Adams, “Hearing Musical Streams”, Computer Music Journal 3, No. 4, pp.26-43.
Performances & Broadcasts
* McGill University, Montréal, Québec, Canada 1985
* Studio Recording, Radio-Canada, Québec, Canada 1985
* Radio-Canada Broadcasts, Québec, Canada 1985, 1987