<p> The BMO Harris Pavilion has announced another post-Summerfest concert: Elvis Costello and the Imposters will headline the stage on Saturday, Sept. 15. The long-running joke about Costello is that whenever he releases a new album, record stores never know which genre to file it under. In the past decade or so, Costello has released a roots-rock song cycle, a collaboration with opera singer Anne Sofie von Otter, another with R&B legend Allen Toussaint, a couple albums of jazzy ballads, an orchestral suite and several discs with the Imposters, the latest incarnation of his New Wave-era band the Attractions. He\'s done justice to all eras of his career on his recent tours.<br /></p> <p>Tickets for the show go on sale Thursday, June 21 at 10 a.m. Ticket price information has not yet been announced.<br /></p>