This machine was conceived to build complex forms through repetition, and accumulation of events through delays, filtering and feedback. It consisted of a large rotating disk, 50 cm in diameter, on which was stuck a tape with its magnetic side facing outward. A series of twelve movable magnetic heads (one each recording head and erasing head, and ten playback heads) were positioned around the disk, in contact with the tape. A sound up to four seconds long could be recorded on the looped tape and the ten playback heads would then read the information with different delays, according to their (adjustable) positions around the disk. A separate amplifier and band-pass filter for each head could modify the spectrum of the sound, and additional feedback loops could transmit the information to the recording head. The resulting repetitions of a sound occurred at different time intervals, and could be filtered or modified through feedback. This system was also easily capable of producing artificial reverberation or continuous sounds (Teruggi 2007, 218).
Pierre Henry using induction coils to control sound spatially.
Early sound spatialisation systemhttp://en.wikipedia.org/wiki/Musique_concr%C3%A8te