Happy birthday Amos, all the best.

Here's your presi; a do it yourself very small piece of brain.
If you build the circuit as drawn and feed current into the top rail through a 1M-Ohm variable-resistor (potentiometer) connected to the positive terminal of a 9V Battery grounded to the bottom rail you can listen to the oscillations through an amplifier connected across the Membrane capacitor. Lowering Cm moves the oscillations to a higher, more musically interesting frequency.

Enjoy

PP