The cover of Robert Plant and Alison Krauss' collaborative album Raising Sand doesn't include the name of producer T-Bone Burnett, but he's the one who conceived the project and turned it into another of his periodic meditations on where folk music has been and where it's going. Over the course of Raising Sand's 13 tracks, Burnett, Plant, and Krauss interpret old and new blues, rockabilly, country, and Celtic songs, taking an eclectic approach that sometimes has the music rushing along like progress, and sometimes drifting into the subconscious like a nagging thought. At just under an hour, Raising Sand borders on indulgent sometimes—especially in contrast to the music it's paying homage to—but songs like the dynamic "Please Read The Letter" make good use of every second, and the pleasure of two versatile voices sharing the same wide-open spaces.