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.
The composer Iannis Xenakis (1960) 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. "Granular synthesis has been implemented in different ways, notably by the Canadian composer Barry Truax."
This includes all sounds on the time scale shorter than musical notes, the sound object time scale, and longer than the sample time scale. Specifically, this is shorter than one tenth of a second and longer than 10 milliseconds, which includes part of the audio frequency range (20 Hz to 20 kHz) as well as part of the infrasonic frequency range (below 20 Hz, rhythm).
These sounds include transient audio phenomena and are known in acoustics and signal processing by various names including sound particles, quantum acoustics, sonal atom, grain, glisson, grainlet, trainlet, microarc, wavelet, chirplet, FOF, time-frequency atom, pulsar, impulse, toneburst, tone pip, acoustic pixel, and others. In the frequency domain they may be named kernel, logon, and frame, among others.
- Csound – comprehensive music software including granular synthesis (overview over granular synthesis opcodes)
- Max/MSP – graphical authoring software for real-time audio and video
- Pure Data (Pd) – graphical programming language for real-time audio and video
- SuperCollider – programming language for real time audio synthesis
- Xenakis, Iannis (1971) Formalized Music: Thought and Mathematics in Composition. Bloomington and London: Indiana University Press.
- Roads, Curtis (1996). The Computer Music Tutorial. Cambridge: The MIT Press. p. 169. ISBN 0-262-18158-4.
- Truax, Barry (1988). "Real-Time Granular Synthesis with a Digital Signal Processor". Computer Music Journal. 12 (2): 14–26. doi:10.2307/3679938. JSTOR 3679938.
- Roads, Curtis (2001). Microsound, p. vii and 20-28. Cambridge: MIT Press. ISBN 0-262-18215-7.
- Horacio Vaggione, "Articulating Microtime", Computer Music Journal, Vol. 20, No. 2. (Summer, 1996), pp. 33–38.[page needed]
- "Granular Synthesis" by Eric Kuehnl
- "The development of GiST, a Granular. Synthesis Toolkit Based on an Extension of the FOF Generator" by Gerhard Eckel and Manuel Rocha Iturbide
- Searching for a global synthesis technique through a quantum conception of sound by Manuel Rocha Iturbide
- Further articles on Granular Synthesis
- Bencina, R. (2006) “Implementing Real-Time Granular Synthesis,” in Greenbaum & Barzel (eds.), Audio Anecdotes III, ISBN 1-56881-215-9, A.K. Peters, Natick. online pdf
- Miranda, E. R. (2002). Computer Sound Design: Synthesis Techniques and Programming. Oxford: Focal Press. ISBN 0-240-51693-1.
- Roads, Curtis (2001). Microsound. Cambridge: MIT Press. ISBN 0-262-18215-7.
- Wilson, Scott (2011). The SuperCollider Book. Cambridge: The MIT Press. ISBN 978-0-262-23269-2.
- Iturbide, Manuel Rocha (1999). "Doctoral Thesis: Les techniques granulaires dans la synthèse sonore". ArteSonoro.net. University of Paris VIII.
- Curtis Roads (2004). CD accomanying Microsounds. MIT Press. ISBN 0-262-18215-7. Contains excerpts of nscor and Field (1981). Microsounds at Discogs.
- Iannis Xenakis. Analogique A-B (1959), on Alpha & Omega at Discogs and Music For Strings at Discogs
- Granular Synthesis Resource Web Site