Robert Plant Alison Krauss

"I'm bewildered," Robert Plant said onstage as he accepted the Grammy Album of the Year award with Alison Krauss on Sunday night. "In the old days we would have called this selling out, but it's a good way to spend a Sunday."

He was probably one of the few who were surprised, because Raising Sand, which won five trophies at Sunday night's show, is in many ways the perfect Grammy album. It features two respected veterans, a critically lauded producer, some sandpaper-and-velvet vocals and a baker's dozen of time-tested standards.

You're probably familiar with Robert Plant from his Led Zeppelin days, and you might be aware of producer T-Bone Burnett's work on the "O Brother, Where Art Thou?" soundtrack (it won the Grammy for Album of the Year in 2002). And if you don't know who Alison Krauss is, she possesses a haunting set of pipes and is one of the meanest fiddle players in the world. Oh, and she's won 21 Grammys, more than any other female artist and the seventh-most in history.

Really, she's the key to Sand's success, and not just because of her voice (or her fiddle playing). She and Plant first met in 2004, at a Rock and Roll Hall of Fame tribute to legendary bluesman Leadbelly, and the former Zeppelin man was amazed by her knowledge of American Roots music — so much so that they began kicking around the idea of recording an album together. Three years later, Sand was released.

And while Plant possesses the more famous voice, the album's finest moments radiate from Krauss. Whether she's getting bluesy on Little Milton's "Let Your Loss Be Your Lesson" or entwining with Plant's husky voice on songs like "Please Read the Letter" and Roly Salley's winsome "Killing the Blues," she more than carries her end of the bargain.

And perhaps that's also due to producer Burnett, who handpicked the 13 songs the duo cover on Sand. His arrangements are sparse — giving the two voices ample room to breathe — yet dense, warm and crackling at the same time. It's a testament to his work that he's often given just as much billing as Plant and Krauss on the project ... and it's certainly justified.

To date, Sand has sold more than 1 million copies, heaped tons of acclaim and actually earned a Grammy last year — "Gone Gone Gone (Done Moved On)" took home the award for Best Pop Collaboration With Vocals.

One expert was surprised not by the album's success, but by the fact that it's actually quite a good album.

"At first, the album seemed like a vanity project. ... Two names, clearly a one-off record, didn't have to be any good, you know?" New York Times music critic Jon Caramanica said. "Led Zeppelin fans would buy it because of Robert Plant, Alison Krauss would get a check. But it actually turned out to be a really thoughtful, really good record. So when you combine all that with the fact that the Grammys love to lionize one of their own, I could really see it taking home some awards."