Analog Box 2 : Audio Research : Temporal Coherence : Part 5.1

Temporal Coherence in the Perception of Tone Sequences

Part 5.1:
Random Sequences

With this circuit you can listen to a random sequence in which each tone is a certain step size upwards or downwards from the previous tone. The sequence is then limited to a few octaves of range.

Vary the tempo of the sequence with the 'T slider'. Change the step size from 0 to 20 semitones with the 'step size' slider.

With small step sizes, 1 or 2 semitones, you will always hear a coherent sequence, even at very high rates. At the fastest rate, the tones will seem to fuse together into a continuous, up and down moving tone: the phenomenon of fusion.

At larger step sizes and higher rates, beyond 5 or 6 semitones and 10 tones per second for example, you will notice small clusters of tones loosing coherence with the other tones. These clusters often do not seem to be isochronous. When you sufficiently lower the tempo you can hear that the sequence is indeed isochronous.