Kompoz, which will announce its official launch today, is a collaborative music space combined with social features. Users create "song projects", and others can then add their own instruments to create a track. The basic features include artist profile pages, forums, tagging and the ability to apply Creative Commons licensing to your work.
I gotta say I love the idea, but within 5 minutes of hitting the site, you can see they haven't executed all that well. The interface isn't all that clear, and the expected features - Flash players all over the place, ability to grab tracks and stick them together and so on - just aren't there, or properly implemented.
If you've seen the awe-inspiring site Splice, not to mention the equally impressive Jamglue and YourSpins, you won't be all that impressed by what Kompoz has to offer.