In Zalmen Mlotek's '50s New York household, Yiddish was practically the family business. His parents, Yosl and Chana Mlotek, didn't try to assimilate into mainstream America. They didn't want to shed their Eastern European heritage.

On the contrary, they reveled in it. The Polish-born Yosl and New York-born Chana spoke the mamaloshen (mother tongue) at home, partied with people from the Yiddish theater, debated with others from the Bundist Yiddish socialist movement and sent their son, Zalmen, to Yiddish school and Yiddish camp during the summer.

Today Mlotek, 46, is one of the world's leading authorities on Yiddish theater and music. He composes Yiddish music and performs all over the world. He's produced and done the musical direction for shows off and on Broadway and at regional theater around the country.

"I come from a home where Yiddish was more than a language and a culture. It was a way of life," Mlotek says. "One of the main mandates of the [Bundist socialist movement] was that Yiddish is an important language and culture."

Mlotek is carrying out that mandate, leading a crusade to revive Yiddish music and theater. Just last season, he was musical director for "Shlemiel the First," performed at San Francisco's ACT as well as in Boston and Los Angeles.

On Thursday, Dec. 4, he is returning to the Bay Area in a show, "From the Yiddish Stage to the Klezmer Revival," at the Contra Costa Jewish Community Center in Walnut Creek. He'll be joined by singer Sylvie Braitman and violinist Daniel Hoffman. Mlotek calls it an evening of "edutainment" because it entertains and educates about the past 100 years of Yiddish music.

Mlotek thinks the attraction of Yiddish music is its raw emotion. It's the music that accompanied the lives of millions of Jews for several hundred years.

"Yiddish music has traces of the widest gamut of human emotions. Emotions are not veiled; they are poured out in the music," says Mlotek. "The wail of the clarinet. You hear the rocking of the violin. It's very emotion connected. That touches people who are able to hear music and be affected by music."

With his parents, Mlotek released a Yiddish songbook last spring. "Songs of Generations" is his parents' third songbook. The earlier two are regarded as the klezmer musicians' bible.

Today, Yiddish music is enjoying a new-found popularity and acceptability. Klezmer music, for one, is hot and hip. Solely instrumental and only a small part of the body of Yiddish music, klezmer has enjoyed a tremendous surge recently with bands popping up everywhere. In Germany alone, Mlotek estimates there are 30 or 40.

"I am finding that people are inviting me to speak about Yiddish music at schools and universities which until now would not have considered it," says Mlotek. "[They are] looking at it with a new respect."

To his surprise, the European audiences that come to his concerts tend to be young and non-Jewish.

"They come [to my show] with the same intensity as they go to rock concerts," says Mlotek.

Besides his music, Mlotek's other efforts have been geared toward the theater. For example, along with his cousin, Moishe Rosenfeld, Mlotek produced "The Golden Land" and "On Second Avenue" off-Broadway. In 1991 Mlotek and Rosenfeld took "Those Were the Days," a musical revue of Yiddish music and shtetl life, to Broadway, where it received a Drama Desk Award and two Tony nominations. Mlotek also composed the score for the Showtime movie "In the Presence of Mine Enemies" and has released numerous recordings of Yiddish songs.

Until the middle of this century, every city with a Jewish population had Yiddish theater. On New York City's Second Avenue — the heart of the Yiddish theater district — theatergoers could choose from as many as 20 to 30 shows on any given night. Productions included translations of works by great playwrights to original operettas, comedies and dramas.

Irving Berlin, George Gershwin and many other notables of the American musical theater nourished their creative muses on Second Avenue, Americanized the themes and humor they saw, and exported it to Broadway.

But assimilation and the Holocaust nearly wiped out Yiddish as a spoken language, and with it went the Yiddish theater. However, thanks to a dedicated few like Mlotek, Yiddish music and theater are coming back to life and going mainstream.

Mlotek has even more plans for the future.

"At the turn of the century, Yiddish theater was a very sophisticated form of entertainment," says Mlotek. "Elaborate productions of everything from Shakespeare to Molière in Yiddish to grand-scale operettas."

Mlotek wants to see these operettas produced today with full orchestra, chorus and world-class singers. But first, the music has to be available in arrangements suitable for the opera singer.

"Classical singers who look for music in French, German and other languages don't know about [Yiddish opera] music," says Mlotek. "One of my dreams is to publish a book of Yiddish songs in my piano arrangements [that] a singer could work with. Imagine the part it would play in the world of music."