Grain-by-grain pitch shifting produces chorus, noise, or melodic elaboration depending on grain size

When pitch shifting is applied grain-by-grain (rather than globally), the perceptual effect depends strongly on grain duration and the variance of the pitch shift. Large grains with large pitch variance produce melodic elaborations of the source. Large grains with small variance and overlap produce a multi-voice chorus effect. Short grains (below ~50ms) with large variance create noise bands, as pitch variations become microscopic and the signal dissolves into noise. When grain durations go below about 50ms, the chorus effect turns into a ghostly whisper. This makes grain duration a key design parameter for controlling the character of granular pitch processing.

Examples

Grain duration=100ms, pitch shift variance=plus/minus 2 semitones: chorus. Grain duration=20ms, pitch shift variance=plus/minus 5 semitones: noisy shimmer. Grain duration=200ms, pitch shift=+3 semitones: transposed melody.

Assessment

Describe the difference in sonic result between pitch-shifting with 200ms grains versus 20ms grains. Below approximately what grain duration does a chorus effect dissolve into noise?