And how exactly is this different from any other trade out there?
Plumbers are not born as such, they invest money and time to become skilled professionals; but when they fix your boiler, they don't ask for royalties every time you turn the boiler on, do they? They perform a service, you pay for the service, and everyone's happy.
For example, there is no reason why the entire process shouldn't be monetized. A lot of people would pay good money to see those recording sessions, turning a risky long-term investment into immediate profit; the musician would sell a service, like any tradesman.
But no, an "artist" should be able to struggle a couple of years, then watch the money flow in for the rest of his life (plus 70, exactly like a plumber's son... not). Why, it sounds a lot like rent-seeking, that most laudable of economic forces; should we really promote it with such draconian laws?
Btw, to go back about your point about good music being scarce: music that fits the mainstream canon developed by a certain industry in the last 50 years is indeed scarce, probably because it was developed around a model based on scarce distribution resources -- so you over-design one item and make it as marketable as possible to a wide demographic, because your distribution costs are high so you want to make them as repeatable as possible (i.e. you want to make one album and sell a million copies, not ten albums selling a hundred thousand, because you have to modify the physical production line for each album and re-do the whole marketing push through centrally-broadcasted mass-media).
In a world where such limitations are gone, music tastes will develop in different ways. The over-produced album has already been done with -- people buy single items now. Over-production of those single items will probably change as well, as people want faster and faster "updates". Changes in broadcasting are fragmenting tastes, making it very difficult to appeal to everyone, so the "waterfall model" of music production is producing increasingly diminishing returns. The industry will have to move to different models, like quick iterations (you write a song while you tour, and modify it depending on public reaction).
What's so "wrong", so unbearable about all that ? The fact that the Rolling Stones might get a reduced pension? Yeah, they really should be rewarded for ransacking the blues tradition...