Could this not also be solved by a speculative market for songs, sort of like what is described here for an autonomous Associated Press for article content?

http://wiki.bitshares.org/index.php/Potential_DAC_Ideas#Asso...

So as in, you pay a bit to create a market, and buy a bunch of shares low (because you think your song is awesome). Those who find it early and think the price will go higher will buy more shares, and share the song widely so as to increase the chances of others buying in higher. You eventually sell your original shares when you think your song is at it's peak, and make a pretty penny.

Maybe you sold too soon, or too late, but you learn for next time. Maybe you should've kept some for a decade later, at which point some future DJ samples your song and it becomes popular again and the share price starts inching up. Maybe you, as the artist, farm out this speculation part, because -- hey -- you're just interested in making music, and that middleman music trader takes a cut of your earnings :)

Doesn't that give most of the positive effects you mention, but without the notion of copyright?