Pedro Pascal has described Behemoth! as the "hardest" project of his career.

The 51-year-old actor leads the cast of Tony Gilroy's new movie as renowned cellist Alex Serian and explained that the process of learning how to play the instrument made it one of the most difficult films he has ever worked on, although the nature of his character made it "rewarding".

Pedro told Variety: "I would say it's the hardest thing I've ever done, because of the cello. But it was also the most nurturing and rewarding experience: playing someone so private, with a camera on him and knowing that everything he doesn't share with the people orbiting him in the story is being shared with the audience.

"It's an interesting kind of present vulnerability that you had to show up for all the time. As recessive as he may feel, the audience is with him.

"I can't hide anything from you guys. Anything he doesn't understand himself, even if he's looking at something that's a big reveal and we as an audience aren't meant to know what he's seeing, because he doesn't know how to process what he's seeing in that moment."

The Last of Us star had never picked up a cello before production started and confessed that he was dreadful at playing the instrument to begin with.

Pascal explained: "I'm bad at a lot of things. If you could hear it, you would think I was killing an animal.

"You can't just let the bow slide up and down the strings. It has to be primed to press against the string and attempt to play the note. But to marry all of it, the bowing with the fingering and the different positions and the vibrato, is a lifelong endeavour that lifelong cellists are struggling with to this very day.

"My teachers suffer at the hands of it even now. So it was a highly, highly, highly intense lip-sync, shatteringly difficult and I felt back-footed the entire time."

Pedro detailed how he spent an "intensive period" practicing the cello last year before Behemoth! had even been greenlit.

The Mandalorian actor said: "I had an intensive period before we started shooting. I had lunch with Tony in late July, and we started toward the end of October.

"Before anything was signed, as soon as I understood there was a green light, whether it would fall apart or not, I didn't care.

"I went straight into my lessons with Timothy Loo and Charlie Tyler, these incredible musicians.

"Then when we started shooting, whatever window we had, whatever lunch, whatever short day, weekend, I was learning the next thing and the next thing and the next thing. It was crazy."