Former Led Zeppelin singer Robert Plant is teaming up with bluegrass star Alison Krauss for an album of cover songs. The pair, who met seven years ago and played together at a Leadbelly tribute concert in 2004, has been planning to record new disc Raising Sand for years. Among the songs tackled are Gene Clark's Polly, Tom Waits' Trampled Rose and Please Read The Letter, which originally appeared on Plant's 1999 album with Led Zeppelin guitarist Jimmy Page, Walking Into Clarksdale. Raising Sand is due for release in October (07).