Two American musical icons meet on the sixth Masterworks program of the season. Copland’s Shaker-influenced Appalachian Spring and Gershwin’s jazz-infused An American in Paris bookend the concert. Heitzeg’s Symphony In Sculpture celebrates the Pappajohn Sculpture Park through its musical evocation of Des Moines’ favorite sculptures. Margaret Bonds’ Music from the Montgomery Variations reflects the struggles and triumphs of the Civil Rights Movement.