This is just the first in many sites that will be coming from The Chrome Experiment.
The idea here is that there is a steady flow of tiny ball being dropped. You can create lines for these balls to drop on. When you do they bounce and make a musical note. The distance the ball has to drop and the speed it is going changes the sound it makes. You can draw as many lines as you want. There are also controls for the gravity pull, how often a ball drops, and to completely reset the screen and settings.
I really do like this site. It is a lot of fun with no reason to why. Just remember that it is Java Script, so if you go to extreme with your settings, it will slow down.