I think what will be interesting is as thousands of tunes age, with all manner of ownership, presumably some percentage of songs we've all played and know backwards will become Public Domain. . . as if in this day of digital file sharing anyone really 'owns' them as before in the analog age.
I often wonder how much of the constant touring of very 'mature' artists (I think of Paul McCartney, for instance) is due to the collapse of record, songwriting, and airplay royalties. Of course, if I'd been able to afford Paul's ticket prices for his last two trips to Nashville, I'd have seen a Beatle . . . and a billionaire. All you need is cash . . . .
Joey