Audio d-touch is making a collection of applications for real-time musical composition and performance freely available. Using a web-cam, computer, and printer, you can play sounds using image processing to recognize physical markers. You can visit the site below to get the application which includes a drum machine and a sampling sequencer, both are controlled by spatially arranging physical objects on an interactive table surface. Each object represents a sound, and its position with respect to the surface is mapped to certain playback parameters. For example, the horizontal position of an object represents the timing of the sound.
The system is freely available for download because it is part of an academic research project in human-computer interaction. To make the research successful, they are trying to involve as many users as soon as possible.
You can download software here: d-touch.org
Here’s a video: application at work