How Periphery Scored Two Top 25 LPs in a Week With a Prog-Metal Opera

When the six members of the Maryland progressive-metal band Periphery convened last summer at the home of drummer Matt Halpern, they had only a massive jumble of disconnected songs. When they left that fraught five-hour fireside, they had Juggernaut: Alpha and Juggernaut: Omega, a pair of interconnected concept albums that…