WikiMusic

In principle, open content applies to all kinds of materials, not just words. But it's certainly true that most open content is text-based. The basic problem is coming up with a framework that allows collaboration with other kinds of media. So here's an idea: WikiMusic.

The idea here is collaborative asynchronous recording of music, wherin you record your parts to a music editing software file, then upload it for others to add to. Each version of the file can be left online, so that people can revert back to older versions.