This charming music video from Charlie North imagines creating your own simple music controllers with a piece of paper and a marker. (There’s some similarity to M-Audio pieces there, too.) Of course, that raises another question: could this actually be done?
Computer vision isn’t quite intelligent enough to work out automatically what’s going on here, but it seems to me that you could get a little closer. Another alternative would be using conductive ink or graphite to make the drawing itself a sensor. I’m going to leave you to puzzle out the rest.
It’s technically still a holiday weekend here in the U.S. of A., so I’m going to keep with the whimsical inspiration for the rest of the day.