I find this kind of music utterly marvellous and deeply spiritual.
It was originally English, went to New England then spread to survive mainly in the Deep South.
But this is a truly great poem by Charles Wesley - "And am I born to die?" done by an American Indian choir.
What happens is that the choir breaks into the four voices (treble, alto, tenor, bass) in an inward-facing square. (The music is designed for participation - not passive listening).
First the choir tunes to a chord, then sings the notes in a kind of tonicsolfa, then sings the words: you need to read the words as you listen.
The style is almost wholly based on block chords, with not much in the way of melody.
Lots more on this website