The story behind the laser itself is pretty interesting. It was largely built by people at a hacklab in Toronto. Here's a writeup from another member:

http://www.andrewkilpatrick.org/?p=laser_cutter

During the build, we noticed the sound of the stepper motors was unusually melodic. The sound it made while tracing an arc was inescapably musical.

One night, I just hacked up a Ruby script to translate a simple ASCII music notation into movement commands. This is actually quite simple. Feed rate * DPI gives you pitch and distance / feed rate is note duration. All the axes are intersected to create a single list of movements. When multiple axes are moving, a bit of trig is used to calculate the right feed rate.

The acceleration limits also have to be disabled on the machine.

Here is the code. It should work with any G-code based CNC machine:

https://github.com/jedediah/lasermuzak