It’s not a stretch to say that modern Christian rock owes its very existence to Petra. Formed in 1972, the Indiana band paired faith-fortified words with music that wouldn’t sound out of place on rock ’n’ roll radio. Petra’s real gift, however, was an ability to keep up with musical trends. The band’s early, timely focus on Southern classic-rock boogie and riff-heavy AOR eventually gave way to keyboard-driven ’80s hard rock and slick, gospel-tinged pop-rock. Save for their Christian lyrical focus—evangelical invocations, standing strong against temptation and God’s restorative powers—Petra were indistinguishable from their secular peers.