When starting an unpitched percussion for a drum set, I enter notes on the staff and the sound for that instrument plays fine. When I try and use the alt+ or - (or in combo with shift) the note head does not move.
When I start at pitch percusion with a timp, the alt± works fine. I am using Note Performer so I don’t know if that is an issue.
That’s expected. Percussion notes can’t be moved this way, since those notes are actually different instruments.
Alt± and Alt+= are used to respell the note using the note name below and the note name above: this only works on pitched instruments. But you can use Alt+up arrow and Alt+down arrow to move a note from one percussion instrument in the kit to the one above or below if you need to.