“I’ve been reading about the Oskitone 555Poly which looks like a lot of fun. It is a fully polyphonic sound generator based on one 555 oscillator circuit per key, each one individually tuned to the note you want it to play. Unfortunately my budget for making is unlikely to be able to justify getting one myself, but the full development, build and design details are available on github here and it makes for fascinating reading.
This project is not attempting to “build my own” but I was inspired by the idea of an oscillator per key and so I thought I’d spectacularly miss the point of the Oskitone and attempt to use a microcontroller to give me a tunable oscillator output for as many keys as I could manage.
In the process, I’ve managed full 12-note polyphony (as long as you only need 12 notes in total) on an Arduino Uno. Here is how it works.”