On my walk home from work the other day, I came upon a discarded electric piano keyboard on the side of the road. It looked to be in fairly decent condition except for a layer of dust that had built up on the top of the case; it had probably been sitting inside unused for quite a while. I brought it home, thinking that it was probably broken, but that I would salvage the main keyboard and any other nice working bits inside (including a pitch bend wheel). When I got home, I chucked a couple of AA batteries in a switched it on and voila, working perfectly; all keys in working order, and the USB MIDI interface too.
It seemed like a bit of a waste to rip it all apart, so I got thinking about interfacing something interesting to the MIDI interface. I did a bit of research looking for video games that had been designed with a piano keyboard as an input device: I found a reasonable number of projects involving adapting existing games to use a piano input as a bit of a novelty (i.e. this and this), but I couldn't find much in terms of games that explicitly designed with piano input from the start.
I started off by coding up a relatively simple rainbow fireworks display linked into key presses using pygame running through a laptop connected to the midi keyboard and into a TV via HDMI. I coded little fireworks to go off at horizontal positions corresponding to pitch of the pressed key, cycling through colours in the rainbow and handed it to my five year old son to let him have a bit of fun. He seemed to like it; it was a bit like an experiment for him to see how it worked.
I might end up expanding on this idea: I've found products like this that create a whole game out of playing the piano.
Code available at:
https://github.com/mit-mit-randomprojectlab/midi_piano_visual