Drawing Tool

A tool that allows drawing on the score, either from a mouse click or for fingering tapping on mobile.

Might be difficult to implement, but would be very useful for many applications:  making part annotations if people play from a noteflight score on mobile, non-standard or graphic notation, giving teachers a new way for students to interact with NFLearn assignments ("put marks where the beats are", "connect notes a halfstep apart with upside-V's", "listen to the recording while looking at the part and circle any out-of-tune notes", etc.)