As Guillermo del Toro’s go-to composer, Alexandre Desplat knew about the filmmaker’s desire to tell his version of Mary Shelley’s “Frankenstein.”

While del Toro loved the story, Desplat admits his own relationship with the iconic character was pretty much non-existent. He had read the book, but says, “I never saw any ‘Frankenstein’ movie.”

This gave him an innocent approach. Before shooting started, Desplat began by writing a few waltzes to find the right tone. “We tried to find the era. Do we go period? Do we go even before Baroque, or do we go electronica? We had to really decide what the sound of the film would be,” he says. Del Toro didn’t want to make a period movie, so Desplat says “we tried not to be too dated.”

Aside from the tone, the key was finding the sound of the Creature, played by Jacob Elordi. In del Toro’s “Frankenstein,” the Creature is pieced together by dead soldiers killed in the Crimean War and the narrative is flipped of who the monster really is.

“We wanted the soul of the creature to be very delicate and fragile, and it would move the audience,” Desplat says. “We chose the smallest, most fragile and most beautiful instrument, the violin. So this huge creature has a sound which is the most pure and most beautiful sound of classical instruments: the silver violin.”

At that point, Norwegian violin player Eldbjørg Hemsing came in. “She brings this pure sound. She doesn’t play romantic, she plays beautiful. There’s no other way of putting it,” Desplat says. “She understands that the melody lines that I write need to be pure, delicate and very much in tune.”

The pureness of the instrument also reflected the pureness of the creature played by Elordi. The Creature’s main theme, driven by the violin, was the first theme Desplat played for del Toro. “I think he liked it,” he says with a laugh.

In the film, the Creature breaks free of Victor Frankenstein’s lab after Oscar Issac’s character tries to kill his creation by blowing it up. The Creature survives and begins his journey. As the Creature evolves, Desplat wanted audiences to feel empathy. To do so, he relied on motifs including one “the one for the mother that will also become Mia’s love theme, because the mother and Elizabeth are the same.” The love theme is subtly played throughout the movie.

For the large, violent scenes like the fire in the tower, Desplat says: “You can really use the motifs and the melodies and make them completely different. They can become bombastic if you add a full orchestra.”

The film doesn’t feature a wall-to-wall score, but Desplat says the key to the music came from “my love for the actors and the characters.” He explains, “I listen to them and I watch them. Sometimes I stop watching them and just listen to them, to their dialogue, and I try to mingle with them. I want the music to be dancing with the actors. By dancing with them, I respect the pace, the range of the voices and the silences.”

In the ending, Desplat kept the score quiet as the Creature helps the ship break free from the ice and turns to watch the horizon. Then, the orchestra comes in “to make it like a real finale of the opera or symphonic poem, where all the instruments gather,” Desplat says.

“As gently as we took the audience into the film at the beginning with the silver violin, now we let the audience go with this huge, lush sound,” he adds.

Listen to the score below.