postscriptum:
I just gave it a try playing the game with an acutal drawing tablet and BOY-OH-BOY is that the way it is meant to be played, WOW!
It's not functioning a 100% because you always "paint" even if your don't touch the screen with your pen, and the lines kinda don't work at all for me, but the general feeling of painting was so, so much more enjoyable for me.
did you set out to make the worlds first drawing tablet controlled rythm game? because you absolutely should!
btw: I'm using a Huion kamvas 13 if that is any help to know