A couple of small examples that build up in stages teaching the basics of Ruby programming and MIDI output.
This was originally designed for use during CoderDojo sessions at The RoundHouse in Camden, London.
You will need the awesome micromidi gem installed see the docs for instructions (https://github.com/arirusso/micromidi)
In order the hear output you will need a midi device listening. If you are on a Mac then GarageBand works perfectly for this. The "Piano" tutorial was tested with the "Grand Piano" and the "Drums" one was done using the "Rock Kit" instrument.