No one could have predicted that a strange and primitive form of gospel music would become one of the South’s most potent cultural exports.

Sacred Harp singing emerged from deep in the annals of Southern history. It was designed so untrained church-goers could sing by sight from hymnals, and it produced an otherworldly, earth-shakingly loud brand of music.

To folks who grew up in the tradition, Sacred Harp means religion. There are others who view it as “acapella heavy metal.” Both groups hear something divine in the music.

Myke Johns and The Bitter Southerner’s Chuck Reese spent a day at the 2015 Georgia State Sacred Harp Singing Convention. They found that what may seem like an arcane corner of Southern musical tradition has managed to bring together people of all ages, races, creeds and nationalities.

“I think that the way that we sing and the way that we face each other as we sing — that we sing with our full voice — we do create a space with our singing that is a holy space,” says Jesse Karlsberg, a young man who was raised in a Reform Jewish family in Boston and now attends a Sacred Harp singing nearly every week. “It creates an experience in the room. When we’re all tuned together, when we’re all in time together, you can’t help but feel that something important and bigger than us is happening.”

The 2016 Georgia State Sacred Harp Singing Convention takes place atBig Creek Primitive Baptist Church in Alpharetta on Mar. 26 and 27.

This story originally appeared in The Bitter Southerner.