Argentinian website Los Aparatos has directions for building a very simple little Theremin project with readily available components. The circuit is based around two transistors, a capacitor, and a Photo-resistor. The case can be made using an old alarm clock with the center opening perfectly suited for the photo sensor and also the snooze button for triggering the circuit. An insert can be placed over the dial to give the instrument more personalized appearance. Fantastic design, check out more details on this translated version of the website.
Q1. Transistor 2n3904.
Q2. Transistor 2n3906.
B1. Battery: Two batteries AA and a holder.
C1. Ceramic capacitor of 0.1 microfarad.
PC1. LDR, resistance dependent on the light.
SPKR: Speaker of 8 ohms per 1W more or less.
J1: Output Jack.
In this short video also found on the website Mateo Aparato demonstrates one basic principle of circuit bending, by replacing a fixed resistor that controls the pitch on a tiny keyboard with a Photo-resistor. All while wearing a box on his head! Enjoy.