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In October 1979, Leonard Bernstein received a fan letter from a high school humanities teacher. Helen Morgan wrote to the celebrity composer-conductor-pianist in hopes he could share the theme that guided his compositions — something she could pass along to her students for inspiration.

"There are far more than one 'central theme' within my body of works," Bernstein wrote in reply. "But if I had to choose one, perhaps the most significant, it would be our search for a solution to the 20th century crisis of faith."

Bernstein's lifelong effort to find that solution through music is on moving, and sometimes surprising, display at Philadelphia's National Museum of American Jewish History in its new exhibit, "Leonard Bernstein: The Power of Music."

Bernstein thrilled millions around the world with his compositions, his theatrical works like "West Side Story" and his over-the-top conducting style before his death in 1990 at age 72. But the focus here is on a lesser-known side of Bernstein: the second-generation American Jew who inspired social progress on and off the stage.

"He lived through very tumultuous times: World War II, the Holocaust, the Cold War and the Vietnam era," said curator Ivy Weingram. "It was a time of great social upheaval, all of which would challenge the many facets of his identity."

His efforts at breaking down racial barriers in casting "On the Town," and addressing racial tensions in "West Side Story" are among the stories told through interactive exhibits, listening stations and video presentations. Also on display are personal items like Bernstein's piano, conducting suit and baton. The display runs to Sept. 2.

It's just one of over 2,500 events around the world celebrating the 100th anniversary of his birth.

A few highlights:

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HOLOCAUST SURVIVOR ORCHESTRA

In May of 1948, 29-year-old Bernstein was on a European conducting tour, and was asked to take a side trip from Munich to conduct a small orchestra of Holocaust survivors living in displaced persons' camp. Asthma prevented him from serving during the war and so conducting the group of 17 players was his first confrontation with the weight of the Holocaust, Weingram said. The event had a lifelong impact on him.

"He cried his eyes out during the concert and after, he wrote home about that experience," she said. When he died, he left behind an unfinished Holocaust opera.

Visitors can see a photograph of him with the small orchestra, a program from the concert and a citation they gave him. A video presentation shows a documentary interview with members of the orchestra on how that day affected them, including violinist David Arben, who later spent 34 years with the Philadelphia Orchestra.

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EAST SIDE STORY

Fans of the immortal "West Side Story," the Romeo-and-Juliet tale set amid Manhattan fire escapes and street gangs in the late 1950s, might be surprised to learn the show was initially called "East Side Story." It was a tale of Jewish and Irish Catholic gang rivalry set on the New York City's Lower East Side, on the eve of Passover.

Weingram says Bernstein and choreographer Jerome Robbins later decided to take a more contemporary approach to the musical, as Puerto Rican gang violence was making headlines in Chicago and New York. A highly amusing side-by-side video compilation shows the legacy of "West Side Story."

An annotated copy of "Romeo and Juliet" is on display, with notes showing the production was an "out-and-out plea for racial tolerance." An early scene outline from "East Side Story" is also on view.

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'MASS' FOR JFK

Jacqueline Kennedy Onassis had asked Bernstein to create an original piece for the 1971 opening of the Kennedy Center in Washington. He chose to memorialize America's only Catholic president with what he called a "theater piece for singers, players and dancers" based on the liturgy of the Roman Catholic Mass. He collaborated with Stephen Schwartz (of "Godspell" and now "Wicked") on the monumental production.

It requires over 200 performers, dancers, a children's choir, an adult choir, a rock band, a gospel band and sets up a complex dialogue between the celebrant, who is supposed to remain steadfast in his faith, and a street chorus that is constantly trying to get him to crumble spiritually.

"Mass" isn't widely performed, and the exhibit offers Bernstein fans a chance to experience the piece through an original film.

His daughter, Nina Bernstein Simmons, said she hoped viewers take inspiration from his lifetime of work.

"You also are capable of sharing your passions with other human beings and making the world a better place," she said.