What Is Granular Synthesis?
In short, granular synthesis is a form of synthesis which brakes a sound into tiny particles ( grains ) and further reorganizes and redistributes them, in order to create a new sound. Undoubtedly, it is a powerful method of sound manipulation which involves control over pitch, speed and formant characteristics independently from one another. In other words, it is a sound grouping process that is operating on the micro-sound timescale.
The History Of Granular Synthesis
It all started in 1946 when a physicist called Dennis Gabor published his work about applying quantum physics methods to the sound signal. With this work he came up with the system that uses grain system to reproduce a sound. In later years Greek-French composer and musical theorist Iannis Xenakis got in touch with Gabor`s work. Soon after, he created a musical application based on that principle. His first works involved granular synthesis created by splicing magnetic tape into very small segments, rearranging those segments and taping the new string of the segments together.
Shortly after that, inspired by Xenakis works, Curtis Roads began experimenting with this idea on a computer. He was the first person to implement granular sound processing in the digital domain. Following that in the mid 1980’s a Canadian composer named Barry Truax began developing a way to create a granular synthesis in real time. Since then granular synthesis has become available to a growing number of musicians.
Time Stretching & Time Compression
They are the basic aspects of this form of synthesis and creating more or less dense clouds of granular audio particles is a further aspect. The basic parameters that can be found in most of the grain generators are :
1. Grain position
Grain position determines the point in the audio file at which creation of grains occurs. When grain Speed is set to “0“ the audio is “frozen“ at that position, with positive speed values the audio stream plays forward, negative values reverse the audio. Furhermore, LFO or an envelope can modulate Grain Position. In this case the “Speed” value is usually set to 0 so that only the modulator determines the direction and speed of the grain stream.
2. Grain speed
As already mentioned above this parameter determines at what speed the sample “play head” runs through the sample. Some granulators use positive/negative speed values to also determine the direction of the grain stream (forwards/backwards).
3. Grain length
With sizes below 50ms the grain stream turns into noise without a distinct pitch. Very short grain sizes below 10ms in combination with some randomization of grain position create more white-noise-like effects. Also, there are ways of achieving sounds that remind of ring-modulation without randomization. If the grain duration is longer than the intervals between the creation of each grain, it will result in a creation of a sustained sound. If it is smaller the sound gets perforated / fragmented.
4. Grain density
Grain density determines the number of created grains over a given period of time. Therefore, the higher the density the more continuous the sound will become.
5. Grain shape
Most granulators offer a variety of shapes applied to the amplitude of each grain. The most common shapes are Hann, Hamming, Triangle, Sine, Rectangular, Blackman Harris, Welsh. Generally speaking, smoother waveforms with round curves create more organic sounding results, while shapes with more right angled forms create more edgy and distorted tones.
6. Grain pitch
This parameter determines the pitch of each grain. Aditionally, Grain Pitch can be randomized within a given range making for some very interesting chaotic grain pitch clouds. They can also be pitch-quantized to certain scales like pentatonic, major, minor, diminished, dorian, etc. which produces tonal grain clouds.
Additional Resource & Source Texts
http://www.granularsynthesis.com/pdf/gabor.pdf
http://courses.cs.washington.edu/courses/cse490s/11au/Readings/SynthesisChapt5b.pdf
