This would be very useful for live gigs!
Let me transpose my midi inputs from my keyboards.
* Show page level transpose
A global transpose, due to the fact of singers as above, to easy transpose the whole show,
* Song level transpose
Letting me play in key of C when the singer like to sing in key of Bb or C#.
* Section level transpose
For easy change of keys with different sections within a song.
The transpose could be done relative so the three levels may be used in combination to form a resulting transpose.
Maybe also viewed or controlled at Perform View.