Is there any UGen that can get a filter to self-oscillate, like turning the resonance up to a point where it starts to self-oscillate?
in sc3-plugins, there is DFM1. haven’t really played around with it, but might be what you are after?
I posted some code for comparing lowpass filter ugens on the mailing list a few months ago, you might find it useful. As I recall, a number of the filters can self oscillate, but you’ll notice not all of them are super accurate with the frequency parameter