arsd.simpleaudio provides a MidiEvent enum, but the one we're more interested here is the midi file format event, which is found in arsd.midi.
This is the main feature of this module - a struct representing an automatic midi thread.
Added January 1, 2022 (dub v10.5). Not fully stablized but this release does almost everything I want right now, so I don't expect to change it much.
An add-on to arsd.simpleaudio that provides a MidiOutputThread that can play files from arsd.midi.