The clock impulse is made really short by adding a low valued capacitor, this then excites an active bandpass filter with lots of feedback, which creates a sine wave that decays over time. The way I understand it, the circuit needs to get excited with very short and infrequent pulses so that it doesn’t start clipping from too much feedback. Just a little tickle.
I obviously didn’t design this circuit, lol. There are plenty of better resources for this type of circuit.
