When these two prodigious vocal talents first performed together at a Leadbelly tribute concert, they vowed to work together again. When I first heard of their improbable collaboration, I feared the worst. Fear not. T-Bone Burnett has steered another masterpiece, featuring key players from his O Brother Where Art Thou? project, uncovering more gems from the Americana-roots songbook. Mel Tillis, Gene Clark, Townes Van Zandt and Tom Waits all get the treatment on Raising Sand. Robert Plant exercises unprecedented restraint, rarely evoking Led Zeppelin…with a few exhilarating exceptions. Although the Englishman rose to fame as a solo blues singer, on Sand he innately adapts to the vocal group stylings of the The Carter Family and the The Everly Brothers. Krauss has harmonized her way to a female record 21 Grammys (the 21st for Raising Sand), so it’s no surprise that once Plant settles into the material, the result is pure joy.