I've constructed a basic dual op-amp LFO as in the below circuit
The variable resistor R5 is used to alter the rate of the LFO, I'm unsure of the exact frequencies, but this is used in an audio application to control a VCA. It runs on a dual rail power supply at +/-9V, and uses 0V as VR. It works fine.
What I would like to do is control the rate of the LFO (currently done by R5) with another, similar LFO running at a different speed, so the overall rate of the LFO is not constant, and some randomness is added, as if a potentiometer were being constantly adjusted.
My question is - assuming I had another LFO as above, how would I use that to control the rate of the first LFO? My first thought was to use a standard BJT transistor, but I am unsure how to implement this. Can anyone give some pointers?