Seven ages of Salome, now at the Metropolitan Opera. Photo: Evan Zimmerman At the end of the Metropolitan Opera’s new production of Richard Strauss’s Salome , the soprano Elza van den Heever stayed onstage to accept the uproarious ovations with a weepy smile and a grateful tap on her heart. That moment of curtain-call niceness came as a shock on opening night, because for the previous two hours she had exuded the kind of casual, carnal evil that zombies would kill for. What powers van den