How to make an optical theremin to play music

Watch as Kipkay from MAKE Magazine shows you how to make something really cool for your music skills, with parts from RadioShack. Everybody's heard of them, but nobody has one or knows how to play one... a theremin. You could be the exception as you see how to build your very own optical theremin to play the air around you. Wait, this is optical which means you'll be making that beautiful music with light, like a flashlight.

Materials from RadioShack:

(2) Phototransistors
0.047µF Capacitor
100µF Capacitors
1M & 10K Resistors
4AA Batteries
4AA Battery Holder
IC Socket
Line Out Connector
PC Board
Portable Speakers
Project Enclosure
TLC555 Timer