Unearthed is, before anything else, a monolith. It's a whopping five CDs of material, four of which are previously unreleased. The first three are outtakes from the four American Recordings albums Johnny Cash recorded with producer Rick Rubin. Disc four is an entirely new album of gospel songs Cash recorded from his mother's hymnal around the time of American III: Solitary Man. The final disc is a compilation drawn from the released albums. It was planned as a tenth anniversary celebration of the Cash and Rubin collaboration that began in 1992, while they were working on a fifth album. It is, effectively, the last will and testament from country music's grandest and most towering and enduring figure, Hank Williams not withstanding. The box was finished and the final mixes were sent to Cash, though he died before they arrived.