The 2011 “Summer in the Square,” at Union Square, provides early morning fitness, family fun for kids and parents, and live music every Thursday until Aug. 11. In the evening, live music is presented, beginning at 6 p.m., from a diverse mix of genres like latin, rock, jazz, and folk and a mix of local and touring bands. The exception was June 30, when three groups performed. One of them, “Million Dollar Quartet,” is based on the grand recording session where legends Elvis Presley, Johnny Cash, Carl Perkins, and Jerry Lee Lewis were brought together.