There are many Americas. Nowadays they barely speak to each other. But during the most perilous years of the last century, one young composer went in search of a sound that melded many of the nation's strains into something singular and new. He was a man of the left, though of no political party: gay, but neither closeted nor out; Jewish, but agnostic, unless you count music as a religion. His name was Aaron Copland. On this July 4th weekend, WNYC’s Sara Fishko tells his story.