You could even imagine an automated system where you buy a song for some two cents and then sell it back after you're done listening to it for a one cent. You could have users make their collections available on a market place and pay them some fraction of the profits you make.

Music bought on iTunes hasn’t had DRM since 2009

Depends where you’re based. Japan had DRM on iTunes for some time and also DRM-free songs on iTunes were a paid upgrade globally for a while too.

The ability to upgrade was only available for songs purchaseable as DRM-free on iTunes. I still have tracks in my library with the DRM because the distributor went out of business, making it impossible to upgrade.

Oh wow. Which tracks?

On Linux nowadays, but last time I was on macOS with iTunes I has an album of Australian folk rock that still had DRM, were still an old bitrate, and not upgradeable to "Plus" (yes, the thing from 2007) or DRM-free.

IIRC, Plus was DRM-free.

Yeah, was so long ago I couldn't remember if they were separate or not.

I think most were but also as I mentioned elsewhere on this page, Japan and possibly other countries didn’t go DRM-free for some time so possibly they had iTunes Plus but with DRM.