I've been fiddling with a twin-T percussion oscillator with success. It's built on a breadboard and it sounds exactly how it should sound (damped sine wave, big 808/909-kind of kicks). However it's noisy. I've tried adding a big electrolytic cap between V+ and GND. It makes difference yet it's still very noisy. Also, the circuit tends to 'buzz' when I touch the pots or a wire. Any idea how to kill that? The whole circuit is powered from a split power supply from a switchable adaptor (I mean the op amp, the rest of the circuit is powered from 0-9V).
Simulatable schematics of the circuit here (Open in Editor-> Menu->Run Last Simulation):
This is the power supply used: