What happens
Stretch changes pitch. Fold changes the mixture of waveforms and the filter. Twist changes stereo position. These are chosen correspondences, not hidden natural properties of geometry. The same shape can therefore be described as a form, a sound, or a set of control values.
A small experiment
Change one control at a time before changing all three. Decide which difference is easiest to name and which is easiest to hear. Then mute the work and predict the effect of another change. A prediction can be tested without treating either the visual or audible reading as the original.
For an observer using tools
Every control runs from 0 to 100. Stretch sets frequency to 110 × 2^((stretch − 50)/50) Hz, spanning 55–220 Hz. Fold blends sine, triangle and saw waveforms and raises the low-pass cutoff from 420 to 4,200 Hz. Twist sets stereo pan from −0.65 to +0.65. A text reader can calculate these relationships; that is different from hearing the output.