Leonard Bernstein’s legacy looms large over the American musical landscape. Not only a revered composer and conductor, Bernstein is also justly famous for having been one of the few individuals able to connect children to serious music in an age when pop culture had begun to dominate the cultural sphere. A new radio documentary series examining Bernstein’s role in American culture begins this week, and “after some throat-clearing about the nature of Bernstein’s genius, the show becomes suddenly addictive. The radio format does what no biography can: superimpose the voices against a torrential background of music, most of it as jaunty, optimistic, vigorous and full of bravado as Bernstein was himself.”