If you're talking about gospel blues, you've got to talk about one of the all-time greatest Delta blues dudes, Blind Willie Johnson, who recorded solely spirituals in the late '20s. His voice was rough-hewn and intense and his playing knife-sharp and telepathic; if you're already a fan of Bukka White and Charley Patton, you absolutely need to hear this. (And if you're not, you may want to check the sound samples first to make sure it's not too intense!) "Dark Was the Night," which mimics a sermon with moaning and slide guitar, is surely among the most chilling songs ever recorded.