Bob Pittman has always loved splashy events, and his planned two-day iHeartRadio Music Festival certainly qualifies. Clear Channel says it will stage “the biggest live concert festival in radio history” at the MGM Grand in Las Vegas on Sept 23-24, with Ryan Seacrest hosting hitmakers including Lady Gaga, Coldplay, Alicia Keys, Steven Tyler, The Black Eyed Peas, Kenny Chesney, Jennifer Lopez, Carrie Underwood, Usher and Sting. The goal is to “celebrate the launch of the New iHeartRadio,” Clear Channel’s online radio streaming service, with a festival that will reach “the largest combined U.S. radio and online audience ever,” says Pittman — a former MTV and AOL Time Warner honcho who’s now the No. 1 radio company’s chairman of media and entertainment platforms. The event, he adds, “underscores Clear Channel’s transformation to a dynamic integrated media and entertainment company with an unmatched reach in the U.S.” Video and audio streams will be accessible at iHeartRadio.com and at all websites for Clear Channel’s radio stations. The New iHeartRadio will offer broadcast radio stations as well as Pandora-like free, customized services that will have no commercials at least to the end of this year. Seacrest calls the concert “a once-in-a-generation gathering of artists and fans from all over the country.” Tickets to the live event will go on sale July 16.