Barry Manilow, Long Island's Bruce Sussman work in 'Harmony' on Broadway

When Nassau County native Bruce Sussman first pitched Barry Manilow on a somewhat improbable subject for a Broadway musical — a 1930s German singing group called the Comedian Harmonists that few Americans had ever heard of — the pop music legend quickly agreed.

That was in 1991. The two had been pals and collaborators since the '70s, writing pop hits like “Copacabana” and “I Made It Through the Rain.” Their dream of writing for the stage had been deferred for some time.

“I'll never forget it,” Sussman says, recalling the day Manilow heard an old recording of the group. “He was driving down Sunset Boulevard with the tape on and shouting at me through the phone, ‘I get it! I get it! They're incredible. I've never heard anything like this.’ ”

Now, after more than three decades, three fizzled regional productions, a pandemic and a rejuvenating Off-Broadway run, their musical has finally made it to Broadway, opening in November at the Ethel Barrymore Theatre.

“Getting a Broadway musical up is always hard,” Manilow told the "Today" show. “And we hit every brick wall we could hit.”

“Harmony,” with music by Manilow, and book and lyrics by Sussman, tells the true story of the six ambitious young men in the Comedian Harmonists, a sort of Marx Brothers-boy band mashup, who sold millions of records and appeared in 13 films until the Nazis discovered some members of the group were Jewish. The show is a testament to fizzy melodies, tight arrangements and unexpected detours.

It also marks the end of a long journey for Sussman, one that began unexpectedly at a high school in East Rockaway.

'Dark' days and single moms

Sitting in his apartment in London Terrace, a towering pre-World War II complex overlooking the Hudson River from Manhattan’s Chelsea neighborhood, Sussman, 74, has a quick answer when asked the secret to his 51-year creative partnership with Manilow, 80.

“We know how to collaborate,” he says. “We listen.”

That made a difference in the rehearsal room.

“Obviously this story is so personal to them and it was really beautiful how much they cared,” says Sierra Boggess, who stars as Mary, a wife of one of the Harmonists. “It was always special to see them together. You can feel how much they respect each other.”

They share other things, too. Both are Jewish, and both survived rocky years as kids. Manilow, raised by a single mother and grandparents, grew up poor in Brooklyn. He didn’t come into his own until he was a teenager, when his stepfather provided him with a stack of jazz and Broadway albums and a piano, igniting a passion that eventually earned him 50 top 40 hits, plus a Grammy, a Tony and two Emmy Awards.

Sussman, born in Queens, moved to Plainview when he was about 8, enduring “dark, ugly” days as his parents’ marriage fell apart. They separated, and mom moved young Sussman and his sister to an apartment in East Rockaway in 1961.

He attended East Rockaway High School, where “Rock Rivalry” changed his life. “It’s a unique program that every high school in the country should adopt,” he says.

The annual athletic, academic and creative class competition — begun in 1936 and still going strong today — includes a quiz bowl, sports night and original one-act musical. When it came time to decide who’d write the show, Sussman’s classmates all pointed to him.

“I have no idea why,” he says. “I gave no evidence that this was something I knew how to do.”

But he did it. He wrote his first musical as a freshman, and followed suit his sophomore year.

In 1965, his parents briefly reunited and moved the family to Merrick, where Sussman attended Sanford H. Calhoun High School, studying music with the school’s first choral director, S. Talbot Thayer.

“ 'Tal' was driven, demanding and BELOVED. All caps. Full stop. He was one of those teachers who inspired,” says Sussman. “If he’d been a geologist, I would've become a geologist. When people talk about the value of teachers, they don't even begin to describe how valuable teachers can be to the development of a young mind.”

He counts himself lucky.

“The first baby steps I took as a writer happened in Long Island schools,” he says. “I got one of the great educations — it was academically rigorous and actually fun.”

Broadway bound, and then not

While at Calhoun, Sussman’s girlfriend at the time suggested they see the then new hit musical “Man of La Mancha.” It was his first Broadway show. And he was hooked. “I didn’t know what hit me,” Sussman recalls.

After college, Sussman moved to New York City with dreams of finding a composer and, together, writing for the theater.

He attended the BMI Lehman Engel Musical Theatre Workshop, an acclaimed training program for aspiring musical makers. His class included Ed Kleban (future lyricist for “A Chorus Line”), Alan Menken and Howard Ashman (“The Little Mermaid,” “Beauty and the Beast”) and Maury Yeston (“Nine,” “Titanic”). Alas, Sussman didn’t find his composer there.

It happened by accident in 1972. An aspiring singer handed him a demo tape. “The singer was OK,” he says, “What really impressed me was the material, played with great flair at the piano.”

He learned that the songs, arrangements and accompaniment were all by some guy named Barry Manilow who worked in the CBS mailroom. Young Manilow had by this time written an Off-Broadway musical, and was music director for an up-and-coming singer named Bette Midler. Sussman and Manilow met at a nightclub soon thereafter and became fast friends.

“My initial impression was that he was instinctively talented and I’d found my theater composer,” says Sussman. “And I had, except then this thing called ‘Mandy’ happened and we went on a big detour.”

Pivot, then back to the plan

“Mandy,” Manilow’s first No. 1 hit, changed their trajectory. Manilow became a superstar, and he and Sussman wrote more than 200 songs together. But the original plan — Broadway — never quite materialized until now.

Over the years, their writing process has generally remained the same. It’s not music or lyrics but the idea and purpose of the song that comes first. “We try to push the other in the pool,” says Sussman. “I'll say, ‘Do you have a vamp?’ He'll say, ‘Do you have a title, a lyric?’ ” One dives first, and the back-and-forth process begins.

Reminiscing, Sussman is amused by a fun fact. “La Mancha,” his first time at a Broadway show, was technically not on Broadway. That is, not in an official Broadway theater. That show had a Broadway contract but debuted at a venue downtown.

Eager for more, the teenage Sussman hustled to a Broadway ticket desk that used to exist at the Macy’s store in Roosevelt Field, choosing a pair of Peter Shaffer one-act plays, “Black Comedy/White Lies.” This would be his first time in an actual Broadway house. It was the Ethel Barrymore, the same theater where “Harmony” just made its Broadway debut.

Though it took him longer than expected to get here, for Sussman, it’s like coming home. “Only now,” he says, “I have much better seats.”