myvirtualband.com (2005 or so). It was essentially a forum plus an ftp server. The idea was people would record some tracks, upload to the ftp server, and start

myvirtualband.com (2005 or so). It was essentially a forum plus an ftp server. The idea was people would record some tracks, upload to the ftp server, and start a thread, then other people would add on to the track and build up a song or several songs. Everything was by default CC-BY-SA licensed. Also everything was very open, you could see all the threads and all the parts, there weren't any private threads. There are other things kind of like it still (it got sold and became kompoz.com, but that's very very different and not at all the same -- it's much more focused on "bands" and not on freewheeling collaboration, or at least was like that last time I looked.)