Leonard Bernstein was the award-winning conductor and composer of music for West Side Story as well as dozens of other works.
Aside from his work on Broadway, which infused new energy into the medium and influenced many conductors and plays after him, Bernstein was a hardworking social activist.
He wrote an article for The New York Timesin 1947 that contradicted the common sentiment that African Americans were largely absent from the world of classical music because they were incapable of appreciating or creating classical music. The problem, he realized, was pervasive discrimination and lack of access to educational resources: “Everything we do to fight discrimination—in any form or field—will ultimately work toward ameliorating the musical situation,” he wrote.
("Causes and Effecting Change," carnegiehall.org)
Bernstein held many television interviews during his career, being one of the first classical-music aficionados to do so, and used his status as a popular figure to comment on the political landscape. He held anti-nuclear and anti-war views, and was suspected of Communism by the McCarthyist movement. However, his popularity mostly protected him from criticism, at least in the media, and he was able to continue his works until his death in 1990.
Bernstein's main influence on culture was in the world of music and stage plays, to which he added personal and emotional involvement, and popularised classical music to a great extent. He also made it acceptable for behind-the-scenes figures to be vocal about their passions, opening the door for future musicians to become social activists.