- Feedback Knobs - This is found on chorus, phasers, delay etc.
- Dynamic Envelopes - Like a compressor, or dynamic filter, these reference the amplitude of the input to make the sound come alive. Found on V-synth, lots of software FX filters.
- Feedback Oscillator or Loop chain built into a synth - This is found on Dave Smith's designs and also V-synth. This can create circuit overload and clipping sounds.
- Reverb - Reverbs are a type of feedback. The sound is repeated back to you and affected by time / resonance.
Try amplitude modulation or randomization before the inputs. The goal is to find some kind of balance and interesting use of the feedback. The end result is a new sound with some cool time effects. All of the modulation and self referencing will make the sound come alive.
WARNING, this is what happens when you feedback a Roland supersaw wave.