Granular synthesis is a type of audio synthesis that breaks a sound into small particles. After that, this process reorganizes the particles in order to create a new sound. In short, it is a sound manipulation technique that involves sound grouping, pitch control, and speed control.
A Little Bit of History: Granular Synthesis
Around 1946, Dennis Gabor, a well-known physicist, published his work on the application of quantum physics to sound signals. His method used a grain system that was capable of reproducing sounds. Years later, Iannis Xenakis, a Greek-French composer and musical theorist, developed a musical application based on Gabor’s principle. His method involved granular synthesis created by intertwining magnetic tape into segments, rearranging those segments, and finally joining them again.
Xenakis’s method inspired Curtis Roads. Thus, he ended up applying the granular sound processing theory to the digital audio field. Around 1980, Barry Truax, a Canadian composer, developed a technique to create a granular synthesis in real-time. This technique has evolved throughout the years. Nowadays, many musicians use it.
Time Stretching and Time Compressing in Granular Synthesis
Time stretching and time compressing are the fundamental aspects of granular synthesis. There are certain basic parameters to keep in mind, such as grain position, grain speed, grain length, grain density, grain shape, and grain pitch.
Position
Grain position occurs at a specific point of an audio file. When the grain speed is set to zero, the audio is frozen. With positive speeds, the audio stream plays forward, whereas negative values reverse the audio. Plus, envelopes can control the grain position, as well as determine the direction and the speed of the grain stream. This happens when you place the speed value at zero.
Speed
Grain speed is responsible for regulating the speed of the sample. Many granulators use positive/negative speed values to determine the direction of the grain stream.
Stream
The grain stream transforms into noise without a clear pitch when the length of the grain is below 50ms. The combination and randomization of the grain position can create white-noise effects. This usually happens with extremely low grain lengths which fall below 10ms. Ring modulation without randomization is also possible. If the grain length is longer than the intervals that fall between each grain a sustained sound emerges. When the interval is shorter, the sound fragments.
Density
Grain density determines the number of created grains over a specific time period. Hence, the higher the density, the more continuous the sound.
To this respect, grains are available in a wide variety of shapes, including Sine, triangular, Hann, Hamming, rectangular, Welsh, and Blackman Harris. Waveforms with round curves create more natural sounds, whereas waveforms with angled forms create more distorted tones.
Pitch
The grain pitch determines the pitch of each grain. You can randomize it within a specific range to create unique grain pitch clouds. Finally, you can also pithcgrains can also be pitch-quantized to certain scales to produce tonal grain clouds.
Granular Synthesis: Conclusion
When using granular synthesis, it’s best to know all its components to make the best of it. If you want to learn more about other types, you can start by consulting subtractive synthesis, which shares a similar history.
