Perfessor Bill scores his piano pieces with a bass clef and two treble clefs; only the bass clef and one of the treble clefs play the acoustic piano -- the other treble clef part goes to the tone generator. To fix this, open the midi file with MuseScore and:
- Select the first treble staff by clicking on the first note or rest and shift-click on the last one.
- Go to Edit → Voices → Exchange Voice 1-2.
- Select the second treble staff by clicking on the first note or rest and shift-click on the last one.
- Edit → Copy.
- Select the first rest or note in the first treble staff.
- Edit → Paste.
- Go to Edit → Voices → Exchange Voice 1-2.
- Delete the second treble staff, by Create → Instruments, select the second staff and press Delete.
- Export the new midi file with File → Save As, and be sure to select midi as the new file type
The new file has two channels and plays successfully.
Unfortunately, there is no batch method for this.
George