So it's worth asking, is the thing of value here the actual sheet of paper with the music written on it, or the grooved metal cylinder, or the vinyl, or the mp3? Obviously yes, to some extent.
But imagine if you were around in the 1850s and one of your buddies stops by and bangs out "Old Folks at Home" on the piano, totally by heart. And maybe after a couple of times, you kinda figure it out yourself. And then you go to somebody else's house and do the same thing.
Is this the 1850s equivalent of peer-to-peer file sharing?
You start to realize, a song has been bound to a physical object for so long, we've begun to confuse the music -- the actual information -- with the physical object that holds the information. Maybe back in the 1850s there were renegades who ran around teaching people Stephen Foster songs and the publishing companies took a hit and sent the sheriff after them. It seems ridiculous but that's basically what's happening today with the RIAA and file sharing.