I add a photo-resistor to the circuit for some Theremin-like effects.
We are using only 2 pins (one of the 6 inverters) of the 74C14 to make one oscillator, to get a very interesting sounds.
Here is the datasheet with diagram:
www.mouser.com/datasheet/2/30...
In the diagram each triangular symbol is one inverter, each separate inverter can be used for one oscillator.