Earlier quoted context omitted.
What would the business model be in this case?
Someone writes music and sells it to someone who wants to play it. Or maybe someone wants to make a film, so she hires a music writer for the score.
I see the value of copyright (or other intellectual property protection, such as the "terms of use" I mentioned above) in this case, for two reasons.
First, the value for the creative doesn't scale. Suppose a conductor commissioned some music to be written for six summer evening performances. How should the music writer value the work to be written? The negotiations would probably consider how much revenue the performances will generate, and result in a (presumably) fair compensation for the writer.
But suppose the conductor, after the piece has been written, uses the it for eight performances? Or switches to a much larger venue that generates much more revenue? If you don't allow for a way for the writer to be fairly compensated you run the risk of not being able to attract good writers to the field. We could argue that geniuses and top talent would still be there, but it would be difficult for merely talented to make a living (or for the unknown to start out).
The second reason I see is to protect the reputation of the writer. John Williams is a brilliant composer who has written some of the best and most-recognizable movie themes. He wrote, for instance, the theme for the movie "Jaws."
Suppose someone took his music and used it as a soundtrack for a movie that he found very distasteful (a porno, or a movie advocating the rise of the Aryan Nation, for example). He would then be associated with these other ideas, even against his will. You could argue that his ability to use music to conjure emotions could be used to rally people for causes with which he vehemently disagrees. Copyright can help protect against that (but can't completely stop it, of course).