This week I took the MIDI Player that I utilized in my HoloValentine App (get the source code) and put it on GitHub. The source code originally came from a project in CodePlex. The license was a MIT license and the code was originally created for XNA.
I took that and code from folks who had done similar work in Unity and cleaned up some bits to create a MIDIPlayer project that should easily load into any Unity project.
Below is a video where I show checking in the latest change of creating a demo scene that plays a MIDI file on demand. The MIDI file loops, but the MIDIPlayer script can be updated to allow for a playlist. The HoloValentine App shows how to create and play a playlist.
If you are looking to play MIDI files in your Unity project, I hope this helps you!