Image copyright PATHE Image caption Simon Helberg plays a fledgling professional pianist who is dragged into Florence Foster Jenkins' bizarre world

For US actor Simon Helberg being known as a "geek" has served him well. The epithet has, after all, come as a result of his role as Howard Wolowitz in the US sitcom The Big Bang Theory.

The show about a group of highly-intelligent, but oddball friends has been an award-winning hit for almost 10 years, earning Helberg himself a Critics Choice trophy - not to mention a multi-million dollar salary.

Off the back of this success, he's landed a plum gig alongside Meryl Streep and Hugh Grant in the comic - but pathos-filled - Florence Foster Jenkins, from The Queen director Stephen Frears.

It's not Helberg's first film, having had small parts in movies including George Clooney's Good Night, Good Luck and the Coens' A Serious Man.

He's also made and starred in his own semi-auto biographical romantic feature, We'll Never Have Paris.

But Florence Foster Jenkins is undoubtedly a big coup. And his role as Howard can largely be thanked for this, says Helberg.

"I certainly haven't done a film where I've been such an integral part of an ensemble. And you can't get more brilliant and prolific than this ensemble - both on and off-screen," says Helberg.

"Getting to act for nine consecutive years [in The Big Bang Theory] is such an incredible luxury and pretty fantastic practice.

"It's all in many ways led to this, which strangely couldn't be more different from the show."

Helberg plays fledging professional pianist Cosme McMoon in the eponymous Florence Foster Jenkins, the true and extraordinary story of the "worst opera singer in the world".

Image copyright PATHE Image caption Florence Foster Jenkins (Meryl Streep) was passionate about music and put all her energy into her hilariously awful operatic performances

Jenkins, played by Streep, was a wealthy would-be socialite in 1940s New York with a passion for music.

As well as pumping much of her money into supporting the musical life of the city, Jenkins also feeds her own singing aspirations by staging small, elaborately-costumed performances for audiences carefully hand-picked by her partner and protector, the failed actor St Clair Bayfield (Hugh Grant).

Jenkins can't sing, but believes with her enthusiasm and some training she can win through - and pull off a wildly audacious concert at the prestigious Carnegie Hall.

Aided and abetted by Bayfield, whose mission is to ensure Jenkins is never subjected to criticism or ridicule, the film centres on the hilariously off-key and tension-filled preparations for the Carnegie show, which include enlisting the services of pianist McMoon.

"Before the film I knew nothing [about Florence], and there isn't a tremendous amount of existing material on her, aside from some recordings, which definitely gave me some insight," says Helberg.

"When I read the script I ran the gamut of emotions: I laughed hysterically. I cried. It's about a love of music but also a love of life.

"There's a purity to Florence, there's no cynicism, it's all for the music. She's a dreamer. Her story is profound and inspiring."

At the outset, McMoon is blissfully unaware of what he's signed up to. He believes he's lucked out by landing a career-making job as Jenkins' personal pianist. Of course, once Jenkins opens her mouth, the horrifying reality hits home. He wants to run but is ultimately won over.

Image copyright PATHE Image caption Florence Foster Jenkins and her 'protector' St Clair Bayfield were thought of as husband and wife, but never married.

"I enjoy playing characters that feel alien in some ways, which perhaps runs through both Cosme and Howard," says Helberg.

"McMoon is a fish out of water and has no clue what he's entering into. He's fresh off the bus."

"He finds out immediately that he's entered the Twilight Zone and has no idea what is going on. But he shares a love of music with Florence and there is no judgement in him, they both have innocence."

Helberg transmits his panic with wide-eyed charm - and an impressive repertoire of expressions.

"I try to act with my whole body and, for better or worse, this is the face that's attached to it," he laughs.

Ironically, Streep can be credited with being a decent singer - as witnessed in Mama Mia! - and Helberg is a talented pianist.

"Until I was about 16-years-old, my dream was to be a musician," says Helberg. "I played in rock bands and jazz bands. Then I decided to be an actor and kept the stable career of 'jazz pianist' as my safety net."

Image copyright PATHE Image caption Hugh Grant plays the failed actor St Clair Bayfield whose 'forte' was reciting worthy but tedious literary monologues

But attempting to play alongside someone who was singing wildly off-key and off-time was something no training could prepare him for.

"I learned all the pieces to the best of my ability, as they should be played. That made it easier to systematically destroy them with Meryl," explains Helberg.

"I had to know them backwards and forwards in order to really weave in and out of them as Cosme and Florence did. Playing piano well is one thing, but attempting to play at concert level accompanying Meryl Streep, while Stephen Frears is filming you in front of hundreds of people is - well - psychotic."

What ultimately happened when Jenkins played Carnegie Hall, is for audiences to discover. But it can be stated her story is incredible, tragic and inspiring. Its message: The charm of the enthusiastic amateur will triumph.

Helberg acknowledges the pleasure of indulging a passion: "I might love dancing more than I should admit. But not in public," he adds.

Image copyright Pathe Image caption The story of Florence Foster Jenkins also inspired the recent award-winning French movie, Marianne

Despite his blossoming movie career, Helberg says there's no end in sight for Big Bang's Howard.

"I'm not moving anywhere," he states.

"I'm very fortunate to be on a show that people enjoy, and bringing more films into the mix is incredibly exciting for me.

"But next year is season 10. It's surreal. So this has to be at least the halfway mark, right?"

Florence Foster Jenkins is released in the UK on Friday 6 May. We'll Never Have Paris is due for UK release in October.