Sheldon Harnick is best known for penning the lyrics to Fiddler on the Roof, but the 93-year-old collaborated with composer Jerry Bock on another Broadway musical about a Jewish family with five offspring

The much-cherished musical Fiddler on The Roof was based on Sholem Aleichem’s Tevye and his five daughters, but its creators also wrote a companion piece about a father and his quintet of sons.

Just as Tevye battles with his headstrong offspring, so Mayer Rothschild faces both internal strife, and the virulent anti-Semitism of 18th Century Germany in Rothschild and Sons.

The musical explores the humble origins of the family who established an international banking firm while confined to Frankfurt’s ghetto. The endlessly resourceful Mayer does business with the German Court, helps finance Napoleon’s defeat, and uses his leverage to win rights for European Jews.

The musical ran on Broadway in 1970 but Harnick’s reworked, renamed version is at The Park Theatre this month.

“It was originally just called The Rothschilds and it had a romance for one of the sons,” Harnick tells me from his home in the US.

“But I realised the romance was actually between the father and his five sons. From that angle it works in a whole different way.”

Based on a bestselling book, Harnick recalls “having fun” with the musical’s transition from page to stage.

“The source material was colourful, rich and exciting, It depicted the extraordinary success and pressures of this family and was really a celebration of resilience.”

The historic take on German anti-Semitism didn’t just have obvious parallels with the rise of Nazism, but also chimed with the 60s mood, picked up by original script writer Sherman Yellen.

“Sherman was very aware of what was happening in the US with civil rights and he felt the show reflected that. We didn’t think of it that way. With every musical I have ever made, you just find a story that you love and tell it. I was thinking ‘what’s the best way to present this story on the stage so people respond to it?”

Harnick’s own family hail from Austria; his father arrived in New York aged 15 to search for his own father who had abandoned his family.

“I do not come from a wealthy background,” he agrees. “I’m very conscious of my Jewish background and wanted to explore aspects of that.”

He was raised in Chicago where his first exposure to the comic character songs he would make his name with, came from playing violin in amateur G&S productions.

“I really learned from Gilbert’s patter songs, that rapid fire word play inspired me to think about that as a career.”

But at the age of 18, World War II intervened. “I was stationed in Japan, and for those three years in the army I had no particular career ideas, my main idea was staying alive.”

After the war he studied music before moving to New York and starting to write songs for musical reviews. A trip to see the musical Finian’s Rainbow crystallised his life’s passion.

“That’s the piece that first made me want to write lyrics. I loved what the lyricist had done and thought that would be something worth striving for.”

After meeting Bock in the 50s, they collaborated on many projects which gained Harnick three Tony Awards.

“I started writing with another collaborator but everything was an uphill battle, we agreed all the time. I thought ‘maybe I am not a collaborator’. Then I was called in to help rewrite lyrics for a show in trouble. Jerry had just split up with his lyricist and we hit it off immediately, it was such fun working with him, we became friends which really helps.”

Fiddler’s huge success came as “a nice surprise” he adds dryly. “We were prepared to be surprised in the other direction with people rejecting it.” It was when a friend came racing up during the interval saying “this show is about my Irish grandmother” that he knew it was a hit.

“It was that universality that made it such a success. Lyricists are very conscious of rhyme there is a craft to the use of words, and in that, one tries to say something meaningful. At its best, like with Fiddler, it’s an opportunity to say something very deeply believed that you want to communicate.”

Rothschild and Sons runs at The Park Theatre from January 24.