Lady Gaga, Coldplay, Carrie Underwood lead Vegas fete for iHeartRadio

Clear Channel Radio today announced the first ever iHeartRadio Music Festival, promoting it as "the largest concert event in radio history featuring an unparalleled line-up of the biggest names in music."

Hosted by uber-emcee Ryan Seacrest, the action takes place Sept. 23-24 at the MGM Grand in Las Vegas, and promises to deliver a long roster of headliners including Lady Gaga, Coldplay, Alicia Keys, Nicki Minaj, Carrie Underwood and The Black Eyed Peas. Joining them at the MGM will be Kenny Chesney, Rascal Flatts, Steven Tyler, John Mayer, Jennifer Lopez, Jane's Addiction, and Kelly Clarkson, among others, with special performances from Usher and Sting, and more acts to be announced over the summer. Live audio and video streams will be available online and via mobile device, and on all of Clear Channel's radio station websites.

The Vegas extravaganza celebrates the revamping of Clear Channel's iHeartRadio, an online station and mobile device app seeking to combine broadcast radio plus custom stations (think Pandora) in one free service.