This is an interesting SX48 micro-controller midi music maker. You can download the schematics and code on the website. Here is what the maker has to say about the project:

This project uses an SX48 microcontroller at 75 MHz as an 8-channel frequency-synthesis music player with three instruments (selectable per channel): square wave, triangle wave, sinwave. Each channel can play a different pitch. The desired pitch is used to lookup how far to step along the sample waveform each 1/44100 second tick, thereby playing back the waveform at that pitch’s frequency.

More about the SX48 mini MIDI music player

Related:

More about “Craft” 80’s computer audio & video