^ Sorta novel in country music, I s'pose.
No, not really. As I said, it's a well established form of a lineup.
I mean how they have those isolated parts where he's all on his own going "oom pop a oom pop mow mow" and so on.
That one song may have been kind of a novelty. But he doesn't do that in most of the group's music. Either he's singing his proper harmony, or sometimes he gets a line (or even a whole song) on his own. But even if "Elvira" was a novelty, so what? They were just having fun with it. And it worked, since it was a huge hit.
And it's hardly the only song that has weird lines anyway. As anyone who was around for shit like "Bird is the word" and "The Name Game" will attest.