In 2002, Johnny Cash recorded what turned out to become one of his legacy-defining songs. It was unlikely to happen at that point in his life. Cash was seventy years old by then, nearly a decade into a creative revival in a career that saw him go from a superstar and icon to being dropped from his label and playing county fairs, before an improbable rebound back into the zeitgeist with his stripped-down 1994 album, American Recordings. The Man in Black was already a legend at that point—“Folsom Prison Blues,” “I Walk the Line,” and “Ring of Fire” were already firmly established in the cultural canon—but he added a signature song to his catalog with an unlikely cover of the Nine Inch Nails song “Hurt.” Trent…