BallDroppings

"BallDroppings is an addicting and noisy play-toy. It can also be seen as an emergence game. Alternatively this software can be taken seriously as an audio-visual performance instrument. Balls fall from the top of the screen and bounce off the lines you are drawing with the mouse. The balls make a percussive and melodic sound, whose pitch depends on how fast the ball is moving when it hits the line. This delightful application allows experimentation with sound and vision which will compound and intrigue you. Whether you are an adult or child, scientific brainbox or avid gamer. It doesn't have a plot, no heroine, no villain. It has no guns or alien beings. It is simply time to get creative, and those who are creative will love this. --Gosfish Games "

Addicting... You can have multiple instances running at the same time for some interesting sequences. Title link takes you to the site with download. The download is a single exe that runs the app directoy - no install. Now if you could only use it as a MIDI trigger... Via Joe McMahon on SynthSights.