Particle density controls the opacity and transparency of a granular texture

In granular and particle synthesis, density is a prime compositional parameter analogous to opacity in visual art. A sparse cloud (low density) is transparent - other sounds are easily heard through it. As density increases, the cloud becomes opaque, blocking out sounds in the same time-frequency zone. Coalescence is the process by which increasing particle density causes a cloud to transition from a discontinuous, transparent texture into a continuous, opaque tone. Evaporation is the reverse - reducing density dissolves a continuous texture back into a sparse pointillist rhythm. These transitions give composers dynamic control over the solidity and substance of sound material.

Examples

A cloud at 5 grains/sec (fill factor 0.1) is sparse and transparent. At 100 grains/sec (fill factor 2.0) it is opaque and dense. Smoothly ramping density from 5 to 100 produces a coalescence effect.

Assessment

Define coalescence and evaporation in the context of granular synthesis. How does particle density relate to the perceived transparency of a cloud texture?