Robert Plant looked shocked when he walked onstage to accept the Album of the Year Grammy for Raising Sand, his duets album with Alison Krauss. He never won a single Grammy during his Led Zeppelin years, but this was his fifth of the night. "I'm bewildered," he told the crowd. "In the old days, we would have called this selling out — but it's a good way to spend a Sunday."

The duo's Grammy-night triumph capped a banner year. Their atmospheric disc of roots-rock covers, produced by T...