Two of American Idol's biggest successes teamed up in Nashville Sunday night, as Kelly Clarkson joined Chris Daughtry onstage during his concert to sing Tracy Chapman's "Fast Car." The concert became an all-star affair when Daughtry turned it into a flood-relief benefit concert, with Kelly and 3 Doors Down joining the cause, in addition to regular Daughtry openers Cavo and Lifehouse. 3 Doors Down frontman Brad Arnold sang with Daughtry on the Allman Brothers' "Whipping Post", as did Lifehouse's Jason Wade on "Home," as he has been doing throughout the tour.
Chris and Kelly recorded a song together back in 2008, but it was scrapped and never released (or leaked, darn it).
Chris/Kelly "Fast Car", from MyerJo29:
Daughtry/Lifehouse "Home", from MyerJo29:
Daughtry/3 Doors Down "Whipping Post", from binkzack1:
More info about the concert, including the setlist, can be found at USA Today's Idol Chatter.