The Boston Landmarks Orchestra opened its 2013 summer season at the DCR Hatch Shell Wednesday with its annual green concert in celebration of America’s city, state, and national parks. And the program for this “Rhapsody in Green” could hardly have been more enticing: the premiere of “At the River,” by Northeastern University music-department chair Anthony De Ritis, Ralph Vaughan Williams’s “The Lark Ascending,” Johann Strauss II’s “Tales From the Vienna Woods,” and Beethoven’s Symphony No. 6, the “Pastorale.” On a hot, humid night, the BLO performances were a breath of cool air.

De Ritis’s uplifting composition, a setting of the 19th-century Robert Lowry hymn “Shall We Gather at the River,” was big and dramatic, with a touch of Hollywood or the Pops. Myran Parker-Brass, Boston Public Schools’ executive director for the arts, gave the vocal solo heartfelt power and resonance.