https://atari8bit.net/projects/3d-printing/sio2midi-midixelii-cases/

Mytek over at Ataribits.com has been caught by the MIDI bug of late and it has caused all manner of interesting new bits of MIDI hardware for the Atari 8-Bits. One of those devices is the SIO2MIDI, a tiny circuit with MIDI IN/OUT ports that plugs into your SIO port and is MIDIMate compatible, this means it works with MIDIMaze. It’s cheap, simple to make and enables multiplayer gaming, what’s not to like!