At mediAgora, I go on at some length about 'derivative works' and 'source works' until most non-lawyers' eyes glaze over. Today, I heard a great example of exaclty the kind of thing I'm talking about.
Shannon Campbell is a very talented folk singer-songwriter in Pennsylvania, who posts MP3's on her site, including this one - Dreaming of Violets: (Mirrored on my site).

Scott Andrew LePera is a musician in the California Bay Area. He downloaded Shannon's song, and recorded his own accompaniment, giving this:
Dreaming of Violets (redux): (Mirrored on my site).

OK, you say, beautiful music, talented musicians singing together via their blogs,what's that got to do with your media marketplace dreaming?

Lets imagine a world with mediAgora. In this world, Shannon would have registered her song, and set a price for it (say 50 cents, including a 10 cent promotion fee). People who liked the free preview could pay for the high quality one and download it, and tell their friends and so on.

Scott could find this song, record his extra vocals and backing, and register it with mediAgora too. Say he charged 20 cents for the extra work, with a 5 cent promo fee.

I come along and hear the song on his weblog, and I like it , so I pay 70 cents. This gets me both versions of the song. I link to them here, on mediAgora and so on, and suddenly hundreds of people download the songs (note my fantasy thet hundreds of people read my weblog). Shannon gets 50 cents for each, Scot gets his 20 cents, and I get some of the promotion fee, with the rest going to them. I feel good and Shannon has to spend less time waiting on tables

(reposted from the mediAgora blog)