Alice Cooper turned the world’s largest metal festival into his own horror theatre. The shock-rock pioneer played Wacken Open Air in Germany on August 2, 2013, delivering a spectacular main-stage show drawn from a career that stretches back to the 1960s and broke wide open with 1972’s “School’s Out.” The sound leaned on the gritty guitars of Nita Strauss and Ryan Roxie, Glen Sobel’s forceful drumming, and Cooper’s theatrical vocals, fusing hard rock with horror-movie atmosphere. Props did the rest, as he wielded a guillotine, a snake, and a parade of costumes to amplify his commanding presence. Part of his Raise the Dead tour, the set celebrated a revival of his classic sound, and the band played with a fierce energy that reaffirmed his legacy as rock’s great theatrical showman.