There is currently a MIDI module for receiving MIDI notes over Serial, which might help you? https://www.espruino.com/Midi - you'll have to manually wire up a MIDI socket (and level converter?) though.
Sending over Serial isn't implemented but should be pretty easy - it's just a few bytes.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
There is currently a MIDI module for receiving MIDI notes over Serial, which might help you? https://www.espruino.com/Midi - you'll have to manually wire up a MIDI socket (and level converter?) though.
Sending over Serial isn't implemented but should be pretty easy - it's just a few bytes.
There is also MIDI over Bluetooth LE which might work for you pretty well: https://www.espruino.com/BLE+MIDI
No extra wiring needed - just use a Bluetooth LE Espruino board and you're sorted