For those wanting a simple and interesting project to introduce someone to the world of Arduino - this could be the ticket. Instructables user 'gwarbeh' has created a theremin (a musical instrument that is played without physical contact) using a light-sensor, Arduino and headphones for audio output. You can make it in less than half an hour, and the results are quite good - for example:
Looking for a light sensor? Although it can be tempting to use a light-dependent resistor, they're fragile and can give varying results. Instead - consider our LIGHT: light sensor module based around the digital TEMT6000 sensor. It gives consistent and reliable readings, and is incredibly easy to use with our Getting Started guide. For more information and to order, click here!