The boxed set Unearthed, released shortly after Johnny Cash's death in September 2003, contains a version of Cash's classic song "The Caretaker" in which he asks, "Who's gonna cry when old John dies?" The answer to that question is the millions of fans, admirers, and fellow musicians who have felt the power of Cash's words and voice for the past six decades. His many recordings rank among the best in country music history. Up to the days preceding...