It all started with a gift from his aunt: a used piano. Bernstein received his first piano lessons only at the age of 11, but as exceptional talent he was able to study at Harvard University and also took lectures in philosophy, aesthetics, literature and linguistics. The conductor Dimitri Mitropoulos called him "genius boy" and advised him to continue his studies with Fritz Reiner at the Curtis Institute of Music in Philadelphia (Pennsylvania). Bernstein was able to prove his talent in November 1943 when he jumped in at short notice for the diseased Bruno Walter at Carnegie Hall. The performance of Schumann's Manfred Overture and Strauss' Don Quixote was broadcast nationwide on Broadcasting and a "spectacular" prelude to his musical career. Soon, Bernstein was able to conduct numerous concerts with world-famous orchestras. He was the first US music director of the New York Philharmonic Orchestra (1958-1969), a regular guest conductor of the Vienna Philharmonic and the Symphony Orchestra of Bayerischen Rundfunks. His repertoire included classical as well as avant-garde works - especially the work of Gustav Mahler found his attention and admiration.

Bernstein contributed significantly to the musical education, among others his television series Young People's Concerts (concerts for young people) and the New York Philharmonic Orchestra. His charisma coupled with his great talent for languages ​​and his humor inspired both children and adults alike. With works of classical music he explained basic concepts such as key, melody, modes and impressionism or introduced composers and works (Gustav Mahler, Beethoven, etc.). At Harvard University, he gave a six-part lecture series, The Unanswered Question, in which he spoke about the fundamentals of music in analogy to Noam Chomsky's linguistic research.

As an American Jew, Bernstein was a highlight of the celebration to honour the fall of the Berlin Wall. In the fourth movement he made the choir sang freedom instead of joy - thus turning the ode to joy into an ode to freedom. "I'm sure Beethoven would agree" Bernstein said. The concert has been televised in over 20 countries.

Bernstein was closely associated with Bösendorfer; whenever he was in Vienna, he liked to visit the Bösendorfer selection salon. On his own Bösendorfer, Model 225 with the extra bass keys that could rattle the windows, he composed the opera A Quiet Place and wrote: "How I love this Bösendorfer! Thank you ..."