I’m going to make a “Jingle Bells” based track. Can I register it to PRO?
As far as I know you own the rights on your «recording», but the song is in public domain, so the registration process can vary for different PRO. I’d ask the PRO on how they handle such things.
It depends on PRO probably. In Zaiks you can register it as a kind of your arrangement (in this case you will be the only one author) but you will need to create an old fashioned paper score.