The Everly Brothers recorded the original version in 1964, but it was the chemistry between Plant's urgent gasps and Krauss's bluegrass coo that made their stripped-down rockabilly remake catch fire.
• Robert Plant Opens Up About Led Zeppelin Reunion, Failed Follow-Up With Alison Krauss
• Photos: Rarely Seen Led Zeppelin Photos From "Good Times, Bad Times"
• Rolling Stone's 100 Greatest Singers of All Time: Robert Plant
Random Notes: Hottest Rock Pictures
Video: Exclusive Clip from Hendrix Biopic
Gallery: The Hottest Live Photos of 2014