Hi, just spoiled my answer .. have to learn to operate THIS forum
Just as a short note:
MIDI is NOT intended to be listened to ... When you use a notation program (like Musescore) or a DAW (like GarageBand) you can export your "score" as MIDI ... and you can import it into said programs. It's just a format for interchange of scores i.e. sheet music.
So it's about re-using what the image said or the mp3 made audible.
The alternative is re-entering note by note, which is less than ideal.
So my basic idea is, regardless of implementation:
* see it (image)
* hear it (mp3)
* use it (via MIDI) // it's just some data; as long as it can be stored to some folder, it's fine for the musician