Glimpses of the landscape of American music, as played, sung, and illustrated by projections and narration, will be displayed in a big tent on the headlands at Mendocino, one of the most striking land-and-seascapes on the West Coast. This compound setting for Susan Waterfall’s narrated multimedia program on July 15, “Hallelujah, America!” will be a featured event of the 24th Mendocino Music Festival, July 10-24.