I still have an AOL address, and Apple sent this to it:
Our records indicate that you have been using your AOL Username to sign in to the iTunes Store, App Store, or iBooks Store.
After March 30, 2015, AOL will no longer support your ability to sign in to the iTunes Store, App Store, or iBooks Store. In order to continue using store features, including the ability to access your previously purchased content, you must transition from signing in with your AOL Username to signing in with an Apple ID.
To make this transition, simply sign in once more with your AOL Username to iTunes on your Mac or PC. You will automatically be taken through a few short steps to complete the process.
Well, yeah, I did do that, a decade or so ago. Bought a couple of dozen tracks before getting a proper Apple ID.
And I have no idea if I transitioned correctly; it took me to the usual Apple account screen, where I filled in everything that wasn’t already filled in but didn’t actually change anything on the account.
To learn more about this transition, visit support.apple.com/kb/HT204268.
Well, not much more.