Audio MIDI
You have found the way to MIDI on Audio:
Anthem MIDI Sequencer - A feature packed, easy to use MIDI sequencing package.
MelIDI - Advanced MIDI and Audio sequencer.
Monolith - Freeware MIDI music playback module for RISC OS. Includes a desktop front end.
ReMIDI - Freeware program that will play MIDI files without the need for buying extra hardware. By Michael-Dennis Biemans.
RISC OS abcMIDI - Abc notation is a simple but powerful ASCII musical notation format. Help build the largest human-edited directory on the web.