In synchronous granular synthesis, grain density determines the rhythm-to-pitch transition

In synchronous granular synthesis (SGS), grains are emitted in regular streams with timing controlled by a density parameter. At low densities (0.1-20 grains/sec), the listener hears the individual grain onsets as metrical rhythms, accelerandi, and rallentandi. As density increases above ~20 grains/sec, the onsets fuse perceptually and the stream takes on a pitched, tonal quality. The perceived pitch corresponds to the grain repetition rate. At high densities, the texture becomes continuous. This makes SGS a continuous bridge between the rhythmic and tonal domains, exploitable for gradual transitions or as a performance parameter.

Examples

SGS at 4 grains/sec = quarter notes at 60 BPM. At 10 grains/sec = rapid sixteenths. At 25 grains/sec = onset of tonal fusion. At 100 grains/sec = continuous tone at ~100 Hz fundamental.

Assessment

In synchronous granular synthesis, what determines when a grain stream is perceived as rhythm versus as a pitched tone? Calculate the grain density needed to produce a 60 Hz fundamental frequency.