The site is a grid of various YouTube videos, each a couple of minutes in length, each showing a musician playing a simple Bb major texture. You can play them in any order using as many as you like, starting some as others stop or having them all go at once. It's remarkable. Seriously, don't take my word for it, go check it out now. You won't be disappointed.
Want to participate? Just make a video of your own going by the guidelines on the site and send it in to be included. This can only get more interesting as more videos are added. [In Bb 2.0 via Anthony King]