rate

Declaration

var rate: Float { get set }

Discussion

The varispeed audio unit resamples the input signal, and as a result, changing the playback rate also changes the pitch. For example, changing the rate to 2.0 results in the output audio playing one octave higher. Similarly changing the rate to 0.5, results in the output audio playing one octave lower.

The audio unit measures the pitch in cents, a logarithmic value you use for measuring musical intervals. One octave is equal to 1200 cents. One musical semitone is equal to 100 cents.

Using the rate value you calculate the pitch (in cents) using the formula pitch = 1200.0 * log2(rate). Conversely, you calculate the appropriate rate for a desired pitch with the formula rate = pow(2, cents/1200.0).

The default value is 1.0. The range of values is 0.25 to 4.0.