Their version of “John the Revelator”, while not a cappella, is a show stopper. The version from their 2000 “Live from Mountain Stage” CD is a favorite speaker demo selection of mine. If you don’t think you like the Fairfield Four, try that cut before you rule them out.
On the Ry Cooder soundtrack CD from 1986 “Crossroads” is a blues (once gospel) funeral dirge “Somebody’s Callin’ My Name” sometimes titled “Hush hush…” Jessey Norman also performs this song on one of her CDs. When I die that song is what I want played at my funeral entrance.
On the soundtrack from “The Color Purple” is a song worth your time titled “Maybe God Is Tryin’ to Tell You Somethin’”.
If secular music demonstrates the diversity of the human race so does religious music even more so. On 1992 “Blues Masters, Vol. 04; Harmonica Classics” is Charlie Musselswhite’s hymn “Christo Redemptor”. By any measure it is excellent recording of amazing music.