Arduino Uno and it's many derivatives are very capable devices for many projects. Including some musical instruments and accessorys.
Arduino Uno is based on ATMEGA328 microcontroller, and it's very well documented open source device. Internet is literally full of projects from very simple to extremely complex. I consider myself as an absolute beginner. So if I have done it you can do it too.
I'll show you some random and some musical projects from various sources. These will include clocks, games, musical instruments, peripherals and maybe something else that interest me.
Talking about that... This is all about me and my needs. Arduino projects are perfect way to make something that will suit you. That's how I do these. I'll search for something that's "close enough" for my use, and then modify it as needed. I can claim very very few things as "I created this", so I try my best to credit the original sources when possible.
And last thing: i'll throw in some ESP8266 things as well. Maybe.