I built a piano teacher. I installed LED light on each piano key and turned on and off each of them to show which piano key to press for any given song. (So that any novice should be able to play piano) I don't play piano at all, and this is me playing piano with the help of the device I made. This should not be too hard to build. You will be able to see the instruction manual on how to build this device in 1 or 2 weeks from now. Android app driving the LEDs will be provided as well. As far as I know, no one made this before and I am an amateur, so it had been such a roller coaster ride building this without instruction manuals. But I wanted this device badly enough. It was fun overall. Post your comments here if you have questions.