Robert Plant and Alison Krauss, "Raise the Roof" (Rounder)

Their 2007 duet album "Raising Sand" was a hushed, long-breathed disc with a haunted twang, yet it turned into a blockbuster, winning six Grammys, including album of the year.

It has taken 14 years for a sequel. "Raise the Roof" almost magically reclaims the spectral tone of "Raising Sand," then finds ways to expand on it, delving further into both quiet subtleties and wailing intensity.

Once again, the singers remade songs from a variety of genres — blues, old-timey, soul, country, gospel, rock. Their versions are far removed from the originals, often close to inside-out.

"Trouble With My Lover," an Allen Toussaint composition recorded by Betty Harris, is shifted from a major key to minor, and Krauss trades Harris' New Orleans soul resilience for a neo-Appalachian plaint, lingering over the song's loneliness and hints of betrayal.

Krauss chose "Going Where the Lonely Go," a doleful ballad that Merle Haggard released in the 1980s. Plant recorded a soul song from his teens: "Searching for My Love," by Bobby Moore & the Rhythm Aces. He also brought material from Britain's 1960s folk revival: Bert Jansch's stoically intransigent "It Don't Bother Me," which brings out Krauss' defiant streak; and Anne Briggs' "Go Your Way," a wife's troubled farewell song to a soldier she may never see again.

Plant unleashes his Led Zeppelin wail in "High and Lonesome," which is equal parts biblical and bluesy. At the other end of the dynamic scale is "The Price of Love." The Everly Brothers' own version is an exuberant two-minute, harmonica-topped stomp, though they're singing about a cheater's bitter regrets. Plant and Krauss take the song down to half-speed and remove any distractions. By taking their time, they concentrate the essence of the song. And as they did with "Raising Sand," they calmly defy the impatience of 21st-century pop.

JON PARELES, New York Times