Robert Plant didn't actually have a romance with bluegrass diva Alison Krauss, but between their tender harmonies and the intimate slant of the material, it often sounds that way. They're haunting and heavenly when they join voices on the gospel number "Your Long Journey". Though the stripped-down, acoustic-based sound is a long way from Led Zeppelin, they rock on a slinky version of Allen Toussaint's "Fortune Teller". And when they cover a pair of lesser-known Everly Brothers songs, they sound remarkably like the brothers themselves.