American Idol winner Carrie Underwood, Jamie O'Neal and newcomer Keith Anderson have been added to the cast of a concert to be part of a six-hour special, CMT 100 Greatest Duets. Wednesday's (June 8) concert taping at the Gaylord Entertainment Center marks her first arena performance as well as her live debut in Nashville. Trace Adkins and Terri Clark are co-hosts of the event that will include performances by Dolly Parton, Kenny Rogers, Clint Black, Lisa Hartman Black, Montgomery Gentry, Lee Ann Womack, Shooter Jennings, Joe Nichols, Blake Shelton, Miranda Lambert, Marty Stuart, Travis Tritt, Rebecca Lynn Howard, Crystal Gayle and Raul Malo. The concert will showcase the Top 12 songs in the countdown documentary. CMT 100 Greatest Duets premieres Sept. 17. Tickets to the concert are available at all Ticketmaster outlets and online at CMT.com.