Plant is a Zen master who has always marched to his own flute. So it's almost fitting that he's forgoing a much-rumored Led Zeppelin reunion tour in order to revive the band he fronted in the mid-Sixties. First time around, Band of Joy were a British blues-rock footnote. Now they're an American roots crew in which Plant shares vocal duties with alt-country star Patty Griffin. The first offering from Plant and Band of Joy's forthcoming album, "Angel Dance" is a bluegrass cover of a 20-year-old Los Lobos lullaby, with a sound that recalls Plant's Grammy-winning collaboration with Alison Krauss. Over some mandolin-picking and a fat, subtly distorted low end, Plant punctuates lyrics of fatherly self-assurance ("Goodbye, don't cry/Tomorrow, bring us a brand-new day") with classic predatory aahs and uhhs straight out of "Whole Lotta Love." The result is sweet, elegant NPR folk that still swings like Satan's barn door.