Wobble Bass LFO circuit with Op Amps
What you are looking for is a Voltage Controlled Amplifier (VCA), or a Voltage Controlled Filter (VCF) (which is often implemented using a VCA). These are classic synthesiser circuits and you should have no trouble finding example circuits from these search terms.

A reasonably good inexpensive chip providing dual VCA circuits is the LM13700
whose history is described here 

Circuit here may help you.