Recently I discovered a 'game' on Kongregate called Step Seq. Apparently there are electronic devices that look exactly like this simulation. Their point is to create music on a time and frequency grid. I've been playing around with this one, seen at http://www.kongregate.com/games/quickfingerz/step-seq.
The fun of this is that I've also been video-recording a few of these and have been posting them to Youtube.
The few I've uploaded include an initial boring tutorial and then three more samples. They can be seen with the following links:
I've also created a Youtube playlist for all of my Step Seq. uploads.
View playlist in new window