Our local variant is the Sacred Harp Singing
I've been singing OSH for years and years, my first sing was back in the 1980s at Lacey's Chapel in Henager AL.
The film that this trailer was made from actually features some of the singers at Lacey's Chapel. I saw the film at the Georgia Music Hall of Fame in Macon GA . . . they had a room set up just like a hymn sing, with the benches in a hollow square and everything.
Like they say on the trailer . . . just a wall of sound. Eat your heart out, Phil Spector!
Another handful: http://www.freenorthchurch.org/psalms.htm
Enjoy.