In this Instructable, I'm going to provide a straight-forward schematic and some brief explanations as to how this will work and also some ideas as to what kind of tinkering you can do with this device.
Step 1: Components List
*This resistor can vary between 10k Ohm and 100 k Ohm but other pots (200k or 1M) sound really nice.
470 microFarad Polarized (I prefer something lower than 100 microFarads and I strongly suggest using a 50 microFarad capacitor).
0.01 microFarad non-Polarized)*
*This capacitor can vary between 0.01 microFarads and 0.27 microFarads. I noticed that using a 0.1 microFarad capacitor gets extremely close to a square wave.
8 Ohm Speaker
9 volt Battery
9 volt Connector
Potentiometer (for volume adjustment)