Granular synthesis is a basic sound synthesis method that operates on the microsound time scale.
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It is based on the same principle as sampling. However, the samples are not played back conventionally, but are instead split into small pieces of around 1 to 50 ms. These small pieces are called grains. Multiple grains may be layered on top of each other, and may play at different speeds, phases, volume, and frequency, among other parameters.
At low speeds of playback, the result is a kind of soundscape, often described as a cloud, that is manipulatable in a manner unlike that for natural sound sampling or other synthesis techniques. At high speeds, the result is heard as a note or notes of a novel timbre. By varying the waveform, envelope, duration, spatial position, and density of the grains, many different sounds can be produced.
Both have been used for musical purposes: as sound effects, raw material for further processing by other synthesis or digital signal processing effects, or as complete musical works in their own right. Conventional effects that can be achieved include amplitude modulation and time stretching. More experimentally, stereo or multichannel scattering, random reordering, disintegration and morphing are possible.
History
Greek composer Iannis Xenakis is known as the inventor of the granular synthesis technique. Xenakis was the first to explicate a compositional theory for grains of sound. He began by adopting the following lemma: "All sound, even continuous musical variation, is conceived as an assemblage of a large number of elementary sounds adequately disposed in time. In the attack, body, and decline of a complex sound, thousands of pure sounds appear in a more or less short interval of time." Xenakis created granular sounds using analog tone generators and tape splicing. These appear in the composition Analogique A-B for string orchestra and tape (1959).
Canadian composer Barry Truax was one of the first to implement real-time versions of this synthesis technique.
Graintable synthesis
The Malström synthesizer in Propellerhead's Reason virtual music studio employs a technique known as Graintable synthesis, a technique ostensibly invented by Propellerhead for use in Malström:
Graintable synthesis is neither granular nor wavetable synthesis but a combination of the best of both methods. The results are exciting, controllable and texturally extremely varied. The basis of a Graintable is a sampled sound, which has been pre-processed using an extremely academic and complex method. A whole leaflet would be needed just to describe this. Suffice to say, the result is a perfect set of periodic waveforms that, due to the pre-processing, can be manipulated in a variety of ways. The Graintable can be treated as a wavetable: sweep through it, move through it at any speed without affecting pitch, play any little section repeatedly, use it to pick static waveforms, jump between positions etc.