A feature length documentary about the African-American quartets who traveled the back roads of the Deep South in the 1930s and 40s creating a hard gospel sound and vigorous performing style that foreshadowed doo-wop, rhythm and blues, soul and Motown. With the Dixie Hummingbirds, Blinds Boys of Alabama and Mississippi, Sister Rosetta Tharpe, Soul Stirrers, Fairfield Four, Sensational Nightingales, Mighty Clouds of Joy, Highway QCs and more.