The Leonard Bernstein Collection at the Library of Congress contains more than 15,500 pieces of correspondence to and from Leonard Bernstein. The online collection presents selections of this correspondence dating from 1932 to 1990 that include letters, telegrams, notes, and messages from greeting cards and postcards. The selected correspondence comes from four sources: Bernstein family members; Helen Coates, Bernstein's piano teacher during his adolescence who became his close friend and lifelong personal assistant; Aaron Copland, the eminent American composer, Bernstein's colleague and friend; and Serge Koussevitzky, Bernstein's mentor and a revered conductor and advocate of twentieth century music, and his wife Olga.
Family members whose correspondence is represented includes Leonard's parents, Sam and Jennie Bernstein; his sister, Shirley Bernstein; his brother, Burton Bernstein; and his wife, Felicia Montealegre Bernstein. In most cases, the correspondence includes communications both to and from Bernstein.