acoustic-based backgrounds, such as field recordists, sound artists, and those involved with acoustic design in a variety of contexts, around a common interest in what I have called ‘soundscape composition’ (Truax, 1996). At SFU, this activity evolved spontaneously from the documentation or ‘found’ soundscapes of the WSP. Since most of the participants were composers, they began applying electroacoustic techniques towards processing the recorded sounds, creating compositions that range from those whose sounds are transparently manipulated to those that are much more transformed. However, to distinguish this latter approach from musique concrète and ‘acousmatic’ music, I have argued that the original sounds must stay recognizable and the listener’s contextual and symbolic associations should be invoked for a piece to be a soundscape composition. A recent issue of Contemporary Music Review (1996) devoted to this topic and edited by Katharine Norman was titled ‘A Poetry of Reality’. Music created through soundscape composition cannot be organized with much similarity to instrumental music; in fact, a broader definition of music such as ‘organized sound’ must be invoked if soundscape composition is to be included.

A particularly interesting trend in soundscape composition is the use of multiple loudspeakers for reproducing the work, a performance practice called ‘diffusion’ in electroacoustic circles, originally pioneered in France and now increasingly practiced worldwide. So-called ‘classical’ diffusion takes a stereo image and projects it during the performance into the performance space via multiple loudspeakers, guided by a performer at a mixing console, usually centrally placed. Given the visual and directional bias of most musical performance in theatres – audiences staring at a stage area – this experience is inherently more immersive. However, the stereo source, as developed as it has become, presents a ‘bottleneck’ because of the limitation of two discrete channels.

At SFU we have been creating a multi-channel computer-controlled diffusion system (Truax, 1998) through a collaboration with a local engineer, Tim Bartoo, whose company called Harmonic Functions created an 8-channel prototype unit (the DM-8) and more recently a commercially available 16-channel unit (the AudioBox). The central idea is that a number of discrete source channels of sound can be projected either statically or dynamically onto a number of output channels connected to speakers. Despite the complexity of the signal routing involved, the result can be remarkably similar to situations found in the acoustic environment - discrete sources come from independent directions. There is no natural analogy to the stereo image created through panning where the same sound comes simultaneously from two different sources with varying loudness levels. Even echoes involve a delayed version of the source. The auditory system, presented with this paradoxical effect, resolves the ambiguity by creating the illusion called a ‘phantom image’ which appears to emanate from somewhere between the two speakers (which in the case of headphones means inside one’s head!). However, phantom images are very unstable and even a slight movement off centre from the two speakers shifts the image towards the louder source. In contrast, even just 8 channels of discrete source material (what is technically called ‘uncorrelated’ signals) creates a convincing soundscape where component sounds can be localized in the manner experienced in acoustic environments.