The Grain de Foile uses small slices of sounds (‘grains’) to compose new sounds from existing material. By combining multiple grains of differing lengths, amplitude, pitch and speed new sounds are created which are often very different from the original sound recorded in. Xenakis claims to have invented the technique and indeed his ‘Analogique A-B’, composed of tiny tape splices of pure tones, is credited as the first piece of granular music back in 1959.
In the context of the Z-DSP, a block of memory is set to hold digital samples for playback: the Z-DSP has one second of memory for the audio used in processing. From this audio buffer the grains will sample and modify smaller sections for playback. The number of grains in the process determine how dense the overall output sounds. These programs have 3, 4 or 6 grains for playback. Each grain plays from a random point in the audio buffer and have an independent envelope controlling their duration. The envelope time is the ‘grain size’ parameter in many of the programs.