Asynchronous granular synthesis (AGS) scatters grains statistically across time-frequency clouds

In asynchronous granular synthesis (AGS), thousands of short sound grains (typically 1–100 ms) are distributed randomly within regions called clouds defined on the time-frequency plane. Unlike pitch-synchronous granular synthesis, AGS has no fixed periodicity—grains fire at random times and frequencies within statistically specified bounds. The composer controls cloud parameters: onset time, duration, frequency range, grain density (grains per second), and amplitude envelope. Low grain densities produce sparse, pointillistic textures; high densities produce dense bands of pitched sound or noise depending on frequency spread. Multi-channel spatial scattering further enriches the texture. AGS was pioneered by Iannis Xenakis and implemented in computer music software by Curtis Roads and others.

Examples

A cloud with 50 grains/sec, frequency range 200–800 Hz, and grain duration 20 ms creates a pitched haze. Narrowing the frequency range sharpens pitch; widening it toward a full octave creates formant-coloured noise.

Assessment

Describe how changing cloud grain density from sparse (5 grains/sec) to dense (200 grains/sec) at a fixed frequency range changes the perceived texture, and explain why this happens.