Don't forget that whole genre of songs birthed in the camp meetings of the early 1800s that are often called "white spirituals". Many of the people participating in these meetings were also illiterate, also poor; also seeking to express high octane emotion.

The songs could be as simple as: Four phrases, w/ the first three having the same words [and some kind of melodic sequence]and the fourth, being a "closer". [remember singing "The Paw Paw Patch" as a kid? same deal] [also, the glory, hallelujah refrain of the Battle Hymn of the Republic] Some of those songs did end up in tunebooks like The Sacred Harp, arranged in 3 or 4 part harmony. [Rocky Road comes to mind]

I think, too, that the "floating verse" idea also appears in the Anglo and Irish ballad tradition, doesn't it?

So I guess I don't see ALL that much difference between the camp meetin' choruses back then, and the praise choruses now, except for the probable absence of instruments back then...

But I gotta say, that as a southern don't-know-much-about-polkas girl, I am INTRIGUED by the idea of polka gospel!!!
T