I’ve been playing with Arduinos for a wee while now. These are small microprocessors you can build things with. They use the idea of shields which are small daughter boards that connect to the Arduino to provide extra hardware to do useful things with. One shield I have been playing with the the Adafruit Waveshield. This little board allows you to hook an SD card up to the Arduino and play .wav files from it. These are in mono, 22kHz format. Not HiFi but good enough for little projects. I decided to use one in my old phone to make it play music.
This is about the phone in my old Austin 7 garage where I am building an Austin 7 special. I don’t actually like phones (horrible, nasty things) so this one never actually did anything useful. I used an Arduino and a Adafruit Waveshield to make it into a musical phone playing suitably period songs.