This is a patch written using Pd, also known as Pure Data, the open-source relative of Max/MSP.
Download the patch by clicking on the image above.
There is a nicely put-together downloadable zip file of the Pd application for Mac OS X posted on Samuel Burt's site; it is the latest stable release by Miller Puckette along with organized help files for the extra libraries.
If you run a windows, linux, or other non-mac machine, you will need to download elsewhere; you should be able to find downloadables through one of the sites mentioned above.
In order to get Pd to load the extra libraries (sets of special tools developed for Pd), you will need to go into the Preferences->Startup and put zexy, gem, vasp, and pmpd (one per line) in the list of binaries to load (on next startup). Hit ok when you have done that, and relaunch Pd. The window should look like this:
