Robot Composer
Win a 160-CD complete collection of Bach's music

"On this page you'll find links to sound files (RealPlayer required) for three pieces of keyboard music. One of the keyboard pieces is by JS Bach, another has been generated by a computer, and a third has been written by a living composer in the style of Bach. All you have to do is correctly match each of the pieces ..."

This is quite tricky. I have my own theory, but what do you think?