It's Led Zeppelin played bluegrass-style: Pickin' On Led Zeppelin.
Pickin' On does covers of many different bands and artists. Their cover of Billie Jean is both hilarious and insightful. I love hearing a banjo instead of an electric guitar riff. But their Zeppelin covers are the greatest. My favorites are Kashmir and Babe I'm Gonna Leave You.
It helps that Zeppelin is already so blues-y. But it really comes out in these covers, where vocals are often replaced by a harmonica and violins play backups. Pickin' On's arrangements are seamless and still very true to the original songs. As the album proclaims:
"Whether hillbilly or head-banging, the song does indeed remain the same."