Ludacris is set to release his sixth album, "Theater of the Mind," in September via Def Jam, the rapper tells Bllboard.com. He has been prepping the set while shooting for the upcoming flick "Max Payne."Calling the album a collection of his experiences up to this point, Ludacris promises that "Theater" will be film-worthy. "Expect the whole album [to be] theatrical," he says. Though he hasn't yet chosen a first single, he says that a track should drop by June or July.Ludacris revealed the title of one track, "Let's Stay Together," produced by DJ Paul of Three6 Mafia. Other producers making contributions to the new album include Dre & Vidal, 9th wonder, Ice Drake and DJ Don Cannon...