It’s wild that we ever knew a time before “Seven Nation Army.” Rock was moribund, long in the tooth, a phenomenon that existed in quotation marks and was in need of reviving. And yet nobody had ever put those specific notes in that specific order before Jack White, fucking around at a Melbourne soundcheck one evening, was struck by metaphorical lightning. “Seven Nation Army” is an angry, paranoiac song with no fixed meaning, but it sure sounds like Jack White raging against his own encroaching fame and fantasizing about going to Wichita, far from this opera forevermore. And yet “Seven Nation Army” rocked hard enough to ensure its own immortality. Even if he did go to Wichita, Jack wouldn’t be able to escape his own marvelous big-room banger.