Overall, the electronics for this project are fairly straightforward. Most of the hard work will be happening in the code.
The Feather is acting as the keyboard, it has 12 buttons hooked up to its I/O pins. The Feather has just enough pins, with a few extra to spare. The buttons will represent the notes on a keyboard chromatically: C, C#, D, D#, E, F, F#, G, G#, A, A# and B.
We'll also add an on/off switch by having a switch between the Feather GND and EN pins.
The Circuit Playground Bluefruit is our speaker, or amplifier, for our 8-bit synth. It does have an onboard speaker that we can use, but for maximum loudness we're also going to add a STEMMA Speaker.
The STEMMA Speaker has three connections that need to be made: POWER, GND and SIGNAL. We'll add an on/off switch by using a 3x AAA battery pack that plugs into the JST battery connector with a built-in on/off switch. This will be able to fit inside our 3D printed case.