In this Webel mini-tutorial trail for PureData synthesis you'll find some snapshots of patches used to create the "sound circles" animated logo for the PLAY music/art projects. Each circle (created with PureData/GEM) corresponds to an evolving oscillator frequency with evolving amplitude and pan. There are 8 circles in all, 7 coloured after the optical spectrum, and one white outer circle, giving a composite sound with 1 base frequency and 7 harmonics (in the case where the ratio between frequencies is 2, i.e. an octave).
You can see and hear it in action here: Video: The PLAY synthesised light-sound circles logo (Pure Data + GEM)