The Cake Orchestra uses an Arduino to take analogue readings from a set of light-dependent resistors (LDRs). These happen to be hidden under a set of cakes.
The readings are piped from Arduino into Processing, which uses the Sound Cipher library to generate noises. Each set of cakes has an instrument assigned to it, and each instrument is played at a pitch that reflects the amount of light hitting the LDR.
I played it over lunch (delicious veggie bacon sarnies) at Moseley Barcamp instead of doing a panel - so here's the panel slides I was going to mutter over, plus a demo played by a pelty friend of mine. (no pelt went in the cakes).
It's still quite clunky - it's hard to calibrate for the different settings in which you might want to play it, and I'm not convinced I have the cake -> instrument mappings quite right. Clearly Battenberg is the brass section, but should the Victoria Sponge really be the choir?