Emmylou Harris, Patty Griffin, Shawn Colvin and Buddy Miller (Three Girls and Their Buddy) will perform at Playhouse Square's Allen Theatre. This particular foursome has a well-established history of camaraderie, having been in each other's bands, performed with each other on stage, produced and played on each other's albums, covered each other's songs and turned up at each other's shows many times over the years. Expect an evening of excellence.