I have trouble understanding a lot of this. That's why I am hoping for a lawyer to come in here.
I had Wills' and Poole's songs in mind, when I said that these versions are protected (after 1923), "in their own unique form." At least I hope that the copyrights don't go beyond their particular versions.
The regulations also say something about how "close" a revision may come to an older one, etc., but I quit reading. It all sounds like lawyer Heaven to me. The guy with the bucks can bust the little fellow easily even before he comes to bat.