a number of recent posts have had me revisiting classic FM synth algorithms, and these requests/queries have involved self-modulating "operators" or oscillators. In the classic FM algorithm, we scale the modulator's amplitude as a function of its frequency; despite trawling the web and other resources (including Chowning, and an old Yamaha DX manual) I cannot find a reference to how one should scale the amplitude of the feedback signal in a self-modulating system. If the modulator ratio and index are high (> 1.), as the amplitude of the feedback signal approaches 1. there is a tendency towards noise/chaos. Is there a formula for relating feedback amplitude to modulator frequency that I've missed? The patch below describes the problem:
and I hope the question does not belie the "non-n00b" in the title :)
also, maybe this is just how we get noise in an FM synth?? I fail to see the creative/synthesis value in self-modulation.