The best solution may be a set of co-operating programs, for example use abc to input the tune, a separate scoring program and a separate abc to MIDI program.

Of course, I realise that it may not be that simple, as each may have different restrictions. It is EXTREMELY difficult to manage the notation and performance using the same representation, as they have very different requirements. For example, the notation software does not need to know anything about implied accidentals, but for playback they are essential.