There are several articles which add to our knowledge of the background of folk music. Especially interesting is "The Message of the American Folk Sermon" by Rosenberg. Included is an account of a Methodist and an Af-Am service from 1818.
An excerpt from a Lacy sermon of 1968 (same article) complements a recent thread about the song(s) "Deck of Cards" :

And God
Said there's two ways to go
Heaven
Or either hell
Mister Hoyle
Made a two-spot
He called it a deuce
God from Zion
And put it in the deck
And God
Made the father
Son and the Holy Ghost
Ain't God all right?
And Mister Hoyle
Made a three-spot
And called it a trey
...
I would like to see the rest of that sermon, which appeared in another article.
Oral Tradition, 1/3, 1986, 695-727.

A small part of the journal is on line, they are working on the rest.