This American composer, conductor, and musician was the conductor of the New York Philharmonic for decades, and in that capacity frequently championed under-appreciated (at the time) composers such as Charles Ives and Gustav Mahler. Although he was a serious, academic composer, (writing ballets, symphonies, and operas, among other things), his most famous composition is a Broadway musical that was loosely based on a Shakespeare play.
Leonard Bernstein