LOS ANGELES, California (CNN) -- Robert Plant and Alison Krauss. Once upon a time, the iconic lead singer of Led Zeppelin and the golden girl of bluegrass would never have been mentioned in the same sentence. But since they won five Grammy awards -- including album of the year for their surprising collaboration, "Raising Sand" -- their names have been inextricably linked: RobertPlantandAlisonKrauss. If they were 20 years old and ran in Hollywood circles, tabloids might be calling them Robekrauss or Aliplant. Plant, however, is 60 -- in fantastic shape, and with a full head of the golden ringlets that...