Well, I've been delving back into an old interest I originally pursued in 1992. Now it even has a name: Physical Computing. I found a cool book on the subject at Amazon.com: Physical Computing - Sensing and Controlling the Physical World with Computers by Tom Igoe & Dan O'Sullivan.
Back at school, at MassArt, I was in a program called SIM: Studio for Inter-related Media. One of my projects was a thing called the Sound Square, which was essentially an infrared light-harp, but in a grid configuration. Here are some somewhat dated but amusing video performances. There is also a brief, and incomplete, write up about the Sound Square here.
In short, it's a 7x7 grid of infrared led's and sensors, each beam is about a foot apart, with a simple circuit that allows each beam to be tuned to a different frequency, to avoid crosstalk. Each of the 14 triggers outputs a control voltage. I still have most of the parts, so I figured it might be fun to get it going again.
So 15 years later, I'm checking back into the field of interactive music and it's amazing how much has happened, how much the community has grown, how many new toys there are - yet at the same time it seems that things haven't progressed quite as far as I'd figured they would by now.
In my search for parts to get the Sound Square going, I've been running into some cool stuff, and getting lots of neat ideas foor new projects. Maybe the ole Sound Square will have to wait a while... ;)