It was back in the late 1990s that pop icon Barry Manilow and lyricist and librettist Bruce Sussman first began work on a musical tracing the rise and fall of the Comedian Harmonists, a German vocal sextet featuring three Jewish members that enjoyed great success before Adolf Hitler launched his reign of terror. Since then, the show has been produced in different incarnations at a number of prestigious venues, including Los Angeles’s Ahmanson Theatre and Atlanta’s Alliance Theatre.

“Every time we put the show up,” Manilow notes, “everybody would say, ‘This is the right time for this show, because antisemitism is on the rise.’ Every single time.” But as Harmony prepares for its Broadway premiere at the Ethel Barrymore Theatre, where it’s set to begin previews October 18 and open November 13, that alarm is, he acknowledges, “louder and more frightening.”

Indeed, this production of Harmony, which was introduced Off-Broadway last year at the Museum of Jewish Heritage, arrives at a time when both antisemitism and plays and musicals that tackle that subject have been gaining renewed attention. Sussman muses, “It’s hard for me to believe that four or five years ago everyone said, ‘Let’s do a show that explores Jewish themes and antisemitism.’ That said, I’m not ready to chalk it off as coincidence.”

Sussman points, for example, to last spring’s acclaimed revival of Alfred Uhry and Jason Robert Brown’s Parade, and the upcoming Broadway bow of Joshua Harmon’s Prayer for the French Republic, due to begin previews in December. “I don’t have an answer for it, but I’m happy for it. The theater is always the best forum to examine these issues.”

Not unlike the iconic musical Cabaret, audiences coming to Harmony can expect a balance of heavy subject matters with uplifting musical numbers, delighting theatergoers with Manilow and Sussman’s brand-new musical score.

“We wrote a show that we ourselves would like to see, that is, a show that exp†blores serious themes but also broadly entertains,” says Sussman. “They were, after all, the Comedian Harmonists.”

Sussman was first drawn to the Comedian Harmonists’ story after seeing a black-and-white documentary by the director Eberhard Fechner. He and Manilow, collaborators for more than 50 years, are hardly strangers to musical theater, having adapted their smash 1970s hit song “Copacabana” into a musical on London’s West End in 1994. Manilow had also written music and lyrics for a musical called The Drunkard, which was presented downtown back in 1970, and has contributed songs to Broadway productions, some cowritten with Sussman.

“We had been offered a lot of shows,” Sussman says, “but advice that I got a long time ago is that if you’re going to do this, you’d better love the material, because it’s going to be a long haul. We couldn’t imagine those other shows sustaining us, remaining enthused about them for as long as it takes to put a musical on. This material always spoke to us.”

Music was part of the appeal — in particular, the diversity of the Comedian Harmonists’ repertoire. “Their tagline was ‘From Brahms to blues,’” Sussman points out. “Well, that’s right up our alley. We’re always thinking about how many different styles we can cram into one album. The one talent of Barry’s that I admire most is his ability to write in any musical style you throw at him.”

Manilow adds, “Writing music that’s supposed to come from the ’20s and ’30s — what musician wouldn’t jump at that opportunity?”

“Not all musicians would, Barry,” Sussman interjects. “That’s your unique ability. That’s your weirdness — which I love.”

Their concept for Harmony’s plot, Sussman says, was that the first act would be “the golden-age musical that would have been written about [the Comedian Harmonists] had the events of the second act not occurred.” Hence, Act 1 ends with a character reading telegrams received on the occasion of the group’s triumphant opening performance at Carnegie Hall: “They’re from Fanny Brice and Will Rogers and Gypsy Rose Lee — all of their contemporaries about whom musicals were written.”

For Harmony’s New York production, which is directed and choreographed by Tony Award winner Warren Carlyle, it was decided to add a new character: an older version of one of the singers, called Rabbi, who also functions as a narrator. Sussman wrote two different drafts of the book, one with Rabbi and one without him. “Barry and Warren and I debated for about five of six weeks, because we were attracted to the idea, but it seemed scary to do it for the first time in New York, with the spotlight on us. We decided to go for it because we thought it was an improvement on the piece.”

With beloved veteran Chip Zien in the new role Off-Broadway, the result was a hit with critics and audiences. Zien remains in the cast, along with Sierra Boggess; Julie Benko joins them, fresh off her star-making turn in last year’s revival of Funny Girl. Several others in the company, including actors playing the young Harmonists, are making their Broadway bows.

Sussman is optimistic that the show’s spirit and message, which promote harmony in more than one sense, will have wide appeal. “One of the assistants in stage management is a Venezuelan immigrant, and she was just telling me how much she relates to the piece,” he notes. “I was wide-eyed; that was a new perspective for me. I hope that’s what we’ll be in for, with a lot of people.”