Rock ‘n’ roll hasn’t ruled American pop culture for decades, but in the South, it’s enjoying a renaissance.

From the garage-punk bands of Nashville to Atlanta’s metal-heads, Southern rock scenes are flourishing, sprouting new acts, clubs and publications. The new acts are different from their predecessors: They are multi-ethnic and tackle thorny subjects with a centrist voice. Rather than hiding their accents, they take pride in their Southernness and flaunt it. Musically, they’ve splintered into a variety of styles, from...