Led Zeppelin, Pink Floyd, the Beatles, the Stones, Dylan, Springsteen, Neil Young, the Who, Black Sabbath, AC/DC, David Bowie—the fixtures of my classic-rock youth. But like all precious minerals, classic rock is a finite resource. One day, it will disappear. Bands break up. Albums go unplayed and are eventually forgotten. Legends die. But it still seems . . . unfathomable. For much of my life, I thought that classic rock would be around forever.