First experimental vocal work, Machine 2 specified a route map of possibilities for small chorus imitating then transforming sounds of machinery heard on tape.
Began extensive research on extended human voice in early 1970s, working as improvising vocal performer. One performance can be heard on CD Beach Singularity, while video Trevor by Steina Vasulka, derives from the sounds and faces of another.
Developed sound transformation notation to capture complex and changing vocal sounds, first used in Tuba Mirum, and described in book On Sonic Art. In 1979-80 composed Anticredos for 6 amplified voices using extended vocal techniques for Singcircle: premiered at St John's, Smith Square, London (1980).
1982-88 explored variety of new approaches (tape as environmental backdrop, live electronics, polyrhythm, abstract theatre) in The Vox Cycle, written for Electric Phoenix and commissioned variously by Paris Biennale, Mobius Studio (Boston,USA), IRCAM (Vox 5), the Huddersfield Festival and the BBC Promenade Concerts.
For Vox5, developed new tools for sound morphing, described in Audible Design and available as part of the Sound Loom. The piece Tongues of Fire pushes these techniques to their limit.
In recent pieces, called 'Voiceprints', uses computer to recreate and transform voices of public figures - Mrs Thatcher, Princess Diana in Two Women, Martin Luther King, Neil Armstrong in American Triptych.