Hollywood star Pedro Pascal said learning to play the cello convincingly for Tony Gilroy's "Behemoth!" ​was the most challenging task of his career, joking he would rather relive one of ⁠his most brutal on-screen ⁠battles than learn how to play the instrument again.

Attending the movie's premiere at the London Film Festival on ​Tuesday, Pascal, who plays a talented cellist ​returning ⁠to Los Angeles after nearly two decades of touring, said the role left him more fearful than any previous project.

"I'd never been so afraid," he said. "I've been nervous about other jobs and the physical ... emotional demands, but it was nothing like this."

Describing the challenge, the "Eddington" star joked: "I would choose fighting The Mountain in 'Game of Thrones' over learning how to play the cello convincingly. I would rather be, I don't know, tossed off ⁠a cliff with Nicolas Cage than have to learn how to play the cello."

Despite his fears, Pascal said working with the cello deepened his appreciation for an instrument he had long considered his favorite.

"Once I held the cello, I felt good," he said.

Seventeen-year-old "Thunderbolts*" star Alexa Swinton said working alongside Pascal showed her that success and kindness can go ⁠hand in hand, praising the actor's grace, poise and politeness on set.

Beyond its family drama, "Behemoth!" aims to shine a light on the world of ​film scoring. Gilroy said that, prior to filming, even seasoned members ​of the crew had never stepped inside the scoring stages where much of the work takes place.

The film's ⁠focus ‌struck ‌a chord with the musicians involved in the ⁠production. Actor Eva Victor recalled ‌many telling the cast and crew: "Finally, a movie about us."

The "Sorry, Baby" writer-director-actor ​said the film reveals a vital ⁠but frequently overlooked part of the filmmaking ⁠process.

"I think the curtain will be lifted on something ⁠that's really a huge ​part of film that we don't talk about or ... we kind of take for granted often."