Serge Audio Feedback as Control Signals

Two filters at work, here:
The variable Q with its notch output fed back into vc-frequency, there is a VCA with an offset in the feedback path, and as you crank the feedback from audio into control voltage inputs, the sound takes on the familiar sharp edges, as well as over- and undertones. Where you hear what sounds like a I-IV progression, that’s the variable Q. And you’ll definitely get different behaviors at different resonance (Q) settings, of course.
The variable slope filter handles a simple ostinato from the 555 VCOs. Its BP output goes through an attenuverter and into the filter’s v/o control input. This also yields some interesting harmonics and subharmonics. The difference between positive and negative responses from the attenuverter are pretty subtle, I think, but maybe that’s to be expected. You definitely want attenuation, boost, inversion in the feedback path to make the effect more interesting. The variable slope filter has a fixed resonance, but you can animate the cutoff and slope to mix things up.