Simon Helberg as accompanist Cosmé McMoon in ‘Florence Foster Jenkins.’ (Photo courtesy Paramount Pictures)

Fans who only know Simon Helberg as the super nerd Howard Wolowitz on “The Big Bang Theory” will be surprised and delighted to see him in his latest role: Meryl Streep’s shyly flamboyant accompanist in the new movie “Florence Foster Jenkins,” opening Friday, Aug. 12 in wide release.

Madame Florence, played by Streep, was a wealthy New York socialite and patron of the arts. Although she was a classically trained pianist who played at the White House when she was a child, her claim to musical fame was an infamous 1944 Carnegie Hall performance that showcased her complete lack of singing ability.

Helberg plays Cosmé McMoon, Madame Florence’s long-suffering but supportive pianist. He started developing his character by zeroing in on the work of screenwriter Nicholas Martin.

“First and foremost is the script,” Helberg says. “He wrote these characters who are very vivid and very full. There were so many clues in the script. I took every word and direction as gospel.”

From there, Helberg turned to the historical record, discovering he was born in Mexico to Irish immigrants who later moved to San Antonio and New York.

“I went to research who he really was. There wasn’t a lot of information on him, but there were these little insights,” he says. “I thought he must have felt somewhat alien.”

As for McMoon being gay, everything pointed to it. McMoon was, after all, an accompanist. He was fascinated with muscle magazines and body-building competitions. He worked at a bathhouse and never married.

But Helberg decided to approach the character’s sexual orientation in a subtle manner, reflecting both the character and the period. McMoon starts out the movie “completely innocent.” But, as he starts to move about in the glittering social circles that Jenkins and her husband St. Clair Bayfield (Hugh Grant) inhabit, he becomes more aware of his sexuality. By the end of the movie, McMoon rushes backstage for the Carnegie Hall concert, explaining his lateness by breathlessly gushing, “I was attacked by lots of sailors.” As Helberg dryly notes, it’s not exactly clear what has happened, but “the light bulb has started to flicker.”

As for McMoon’s delightful physical mannerisms, they’re rooted in Helbing’s own training as a piano player: arms weighted to the floor and fingers dancing over the keys. Cosmé, Simon says, “has the posture that a classically trained pianist would be taught.”

Helberg, in fact, nearly became a professional pianist.

“I’m good,” he says. “I used to obsessively play and practice all the time in high school. But once I started acting, then I just started playing for fun. I threw away that career path. Because being an actor is so much easier than being a jazz pianist.”

“I kept playing for fun,” he says, “but never anything classical or opera. Then this came along. I really wanted to be in this movie and thought how great that I can play the piano. At least I’ll be able to put my hands in the right place and make it look real when a classically trained pianist plays the music. Maybe I’ll get to play a song or two.”

But things turned out slightly differently. Director Stephen Frears wanted a pianist who could really play Strauss and Mozart. Once he got the part, Helbing started a crash course in classical music. Then, once he got on set, Helberg started a crash course with Meryl Streep. Luckily, Helberg says, “I’m really good at making people sound worse.”

Streep and Helberg hey had a week and a half to rehearse before filming started.

“We had this great collaboration,” Helberg says. “We really had to go into this intimate and intense training. We had to work it and work it and work it. It was incredibly tough and satisfying to actually sit there and do it.”

Initially, Streep and Helberg assumed they would perform to pre-recorded tracks.

“I know Meryl always wanted to sing it live, but at first that didn’t seem possible,” the actor says. “We prerecorded at Abbey Road Studios, but once we did that, the producers said, ‘Well, they can really do it. Let’s just have them do it live. Screw that album.’”

Working with Streep, Helberg says, “was honestly a dream for me. She’s very aware of people and she’s very open and she’s grounded. She’s about making the best movie she can and it’s not about her. There’s something very effortless about it.”

Since McMoon becomes a confidante to both Madame Florence and her husband, Helberg also spent a lot of time working with Hugh Grant, whom he calls “hilariously self-deprecating and neurotic.”

“I thought that was my job but were battling for who was most neurotic. He was completely consumed with making the film the best it could be. I know he was also nervous about working with Meryl and even Meryl was nervous about being Meryl. That’s a lot of pressure.”

The scene, however, that was must challenging for the actor was McMoon’s delayed burst of laughter after he finally hears Madame Florence sing.

“It’s so hard to laugh that way when you’re having an uncontrollable fit of laughter.”

He asked Meryl Streep for advice, and she said, “Well try to cry, that always makes me laugh.” Helberg rejected that advice, fearing he’d actually cry.

He tried recording a couple of things on his phone, but finally realized, “I just had to surrender to it. Stephen had a conversation with me about how I saw that scene, about how I saw it being shot and how I saw it being cut together, and how I saw the elevator and how many people should be in it. He really was asking me questions that I felt less qualified to answer than he, but he really wanted to know what I thought. It was a tricky scene for everyone involved, but it did turn out nicely.”

Now that “Florence Foster Jenkins” is in theaters, Helberg is getting ready to start filming season 10 of “The Big Bang Theory.” The actor admits he doesn’t know a lot about what’s in store for Howard and his friend.

He says we’ll be seeing more of Christine Baranski, Laurie Metcalf and Judd Hirsch and meet Penny’s brother and mother.

“I literally have no idea.” he says. “They don’t tell us anything ever until we get the script the night before the table read. What I do know, based on my rudimentary knowledge of biology, is that he will be having a baby, because Bernadette is pregnant and I hear that’s how it works. Their baby will come in the first half of the season and they will be navigating that and figuring out who the bigger baby is, him or the baby.”