A. Simple, Yet Powerful-If it uses lots of components then it is too complicated
B. Sound-It's not a a drum machine if it "beeps"
C. Easily Modifiable-If I can't change stuff for improvement it is kind of annoying.
A meticulous internet search wasn't so successful.
Finally, I found this but, even that was a bit un-editable although it was cool. I thought that the samples were a bit small and I for one was not going to rewrite a bunch of samples.
Therefore, I decided to play around with the code and rewrote my own version of it and tweaked it around until I got a sound I liked.
Remember: Make sure you have the Potentiometer on Analog Pin 1 and not Analog Pin Zero. The True Random library uses this wobbly voltage to pick random numbers! MAKE SURE TO FREE UP ANALOG PIN 0!
I drew up a schematic from the code and then made it real.
I know this uses the TX (Digital Pin 1) and RX (Digital Pin Zero) but I had already built a Digital to Analog Converter shield for those pins and was too lazy too build it again.
Step 1: Parts and Stuff.
8 2K Resistors
1 3-Pin Terminal Block