The idea behind it is brilliant. 5 sides of the cube have a button with a picture of an instrument, and the sixth is the full orchestra. When you press the button for an instrument, it plays the part of the song for that instrument. If it's already playing that instrument and you press the button again, it takes that instrument away. It has six or eight different songs, and you press the orchestra button to cycle through them.
Here's a video I found on YouTube that gives a good demonstration of its operation: