With Frozen 2, the long-anticipated sequel to a 2013 smash from Walt Disney Animation Studios, songwriters Kristen Anderson-Lopez and Robert Lopez knew they had a lot to live up to, recognizing at the same time that they couldn’t rest on their laurels.

Winning their first Oscars for Frozen, the songwriting duo have come upon the same question, time and time again, while on the press circuit for Frozen 2. “Every single human being keeps asking us, ‘How did you deal with the pressure of doing this, and following up ‘Let It Go?’” Anderson-Lopez says, with reference to an instant classic written for the first film, which also earned the pair an Annie Award and two Grammys. “And the truth is, the directors we were working with and for immediately said, ‘Don’t do ‘Let It Go.’ We’re going to do a new story, and build it the same way we did the first time, by talking about character very deeply, and getting inspired by our lives now.’”

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Set three years after the events of the first film, Frozen 2 picks up with Arendelle’s royal sisters, Elsa and Anna, as they embark on a journey beyond the borders of their kingdom. Summoned to the North by a mysterious voice, Elsa travels to an enchanted forest—alongside Anna, ice harvester Kristoff, increasingly self-aware snowman Olaf and reindeer Sven—in order to discover the origins of her wintry, magical powers, and thereby save her kingdom.

Reteaming on the sequel with directors Jennifer Lee and Chris Buck, and producer Peter Del Vecho, the Frozen songwriters aimed with this new film not to replicate the original, in all its magic, but to mature it, forcing the franchise’s characters to confront more grown-up questions. Below, the pair discuss the process of doing so, in the writing of seven all-new original songs, and their “six-month odyssey” refining climactic showstopper, “Show Yourself.”

DEADLINE: Both Frozen films have been bold in the depth, darkness and maturity of the stories they’re telling. But clearly, Frozen 2 was taking you both into new territory.

LOPEZ: Yeah. I’m a big Star Wars geek, and I was just hoping, when they first called us, that this wouldn’t be some second-rate sequel, but more like the Empire Strikes Back of Frozen. Some of the reviews have called it that, so I’m really happy.

DEADLINE: The Frozen 2 filmmakers embarked on a research trip to Iceland, Norway and Finland after the film was green lit. Were you there with them?

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ANDERSON-LOPEZ: We weren’t on that trip; we went on a trip a few months before, and came back with all these pictures from Iceland and Norway. I think they went much deeper…We were doing a family trip; they were really on a research trip.

DEADLINE: Where exactly did your journey take you? What did you take away from it?

LOPEZ: In Norway, we went to some of the cities and port towns in the forest. Then, we went to Iceland, which was a whole other landscape. It was so cool to see the glaciers and all that stuff. We were really thrilled with that trip. It was a lot of fun.

ANDERSON-LOPEZ: And the Norwegian forests really do feel like their own character. You can understand why the people of Norway not only came up with these epic tales, but the belief that there are trolls in the forest, because those forests really do feel alive. A glacier really does feel like something ancient and powerful.

DEADLINE: What themes you were thinking about, as you wrote Frozen 2’s original songs?

LOPEZ: One of the quotes that Jen and Chris said early on was, “The two most important days of your life are the day you’re born, and the day you find out why.” That was so inspiring to us, as a lens through which to look at the characters and the story. The end of Frozen was almost like they graduated college; now in Frozen 2, they’re in the real world, and everyone needs to find where they belong. It’s a family that’s together, and is grateful and happy and loves one another, but there’s feelings within each character that have to come out, the way that all feelings do. There’s also mysteries and things in the past that are not alright, not all settled, and the past calls out to be corrected. It involves our heroes, and puts them on this journey.

DEADLINE: Which song featured in the sequel did you write first?

ANDERSON-LOPEZ: The first song we wrote was “All Is Found,” the lullaby that’s sung by Evan Rachel Wood. That was really to try and help us enter this more mysterious, mystical, darker tone, and set the roadmap for the entire movie.

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LOPEZ: It’s a lullaby on one level, but it’s also, in code, everything that the mother needs to tell them from the past. She later passes on; she’s not able to be there when they grow up. So, this lullaby is all they have left of her, these little hints of the past.

DEADLINE: Wood entered the world of Frozen with the sequel. What was it like seeing her bring the lullaby to life?

ANDERSON-LOPEZ: We had written it before Evan was cast, but [a certain vocal quality] was a key factor in casting Evan. She needed to have something that could sound a little bit like Idina [Menzel], a little bit like Kristen [Bell], a little bit different than them both, and she had this wonderful warmth to her voice. We loved that the song, and her voice, is like mist creeping in over the fjord. It has air and mystery in it.

DEADLINE: “Into the Unknown” is a pretty spectacular piece, in which Elsa grapples which the voice from the North that’s been summoning her. How did this song come together?

ANDERSON-LOPEZ: One of the great discoveries, with the story team, with Jennifer Lee and Chris Buck, was that we could put this sense of restlessness in Elsa that was pulling her to her destiny, and dramatize it through this voice. Bobby and I—in studying Norwegian techniques of singing, like joiking and kulning—found this sort of shepherdess-type call that women in the North used to use. The cattle would all recognize a specific shepherdess’s call, and in this case, we’re using a trope that composers have been using for centuries, that usually means destiny and danger.

LOPEZ: At first, we thought that this call would be persistently reaching out to Elsa, and she’d be resisting it. Then, the journey of the song would be a gradual surrendering to the call, and then answering the call. So, it gave us a structure, it gave us a climax, and the song builds to the moment of Elsa singing the call back. They have a moment of duet, and then Elsa finally reaches out with her magic. After that, the events of the movie are really put into motion. It’s this song that catapults and catalyzes the film, after which you can’t go back.

DEADLINE: Who did you have sing the part of the call of the North?

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ANDERSON-LOPEZ: That’s a wonderful Norwegian pop singer named Aurora.

LOPEZ: Tom MacDougall, the head of music at Disney Animation, found her. He played us a couple of different singers who could possibly do it, and everyone loved Aurora. She’s got a wonderful sound.

ANDERSON-LOPEZ: We got to work with her for two days, and she’s a stunning musician. She writers her own songs, and she’s just a musical savant.

DEADLINE: What can you tell us about “Some Things Never Change” and “When I Am Older,” the two songs you wrote for Josh Gad’s lovable snowman Olaf?

LOPEZ: All the songs are thematically linked to this idea of change, and also the idea of the journey, getting lost before you can really be found. Olaf’s song about being by himself in the woods, it’s our first real introduction to the landscape of this forest, where these elements are hiding behind every corner, and it’s a little weird. And Olaf is at a changing point in his life. He was sort of a baby in the first movie, and now he’s sort of a kid, starting to ask the harder questions. But he’s just terrified by this forest, and wishing he was older so he could understand what was going on.

ANDERSON-LOPEZ: We kind of had that as a meta story, because when you’re trying to write these original musicals, you feel like you’re stuck in an enchanted forest you can’t get out of. There’s so many questions, and we were sort of telling ourselves, “This is all going to make sense in six months. This is all going to make sense by the time this movie opens.”

DEADLINE: What was it like to see what Panic! At the Disco frontman Brendon Urie did with “Into the Unknown”? His cover is a testament to his incredible vocal range.

LOPEZ: That was a huge treat for us.

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ANDERSON-LOPEZ: I would just give a big shout-out to Tom MacDougall, who is really our invisible third partner on everything we do. It’s Tom who says, “What do you think of Panic! At the Disco?” And we go, “Yes!” We got to see him record it, and he sang it basically in one take.

LOPEZ: We were nervous about the key he chose, because it’s the same key as Idina’s. But when we saw him do it, we were like, “Oh my God, he can hit that note.”

DEADLINE: What was your biggest challenge with Frozen 2?

ANDERSON-LOPEZ: We were writing “Show Yourself” before we knew exactly what happened at the end of “Show Yourself,” which was a challenge. Because we knew we wanted to tell this story, and broaden the definition of true love. The first movie brought in the definition of true love to familial love, but we wanted to broaden it to the idea of: Sometimes, true love comes in the form of finding your purpose, and your reason for being alive. “Show Yourself” was going to cover that, but it was sort of a six-month odyssey, with ourselves and the story team, and especially Marc Smith, who did the storyboards for it. Because it was a constant chicken-and-egg [scenario], while the rest of the story locked.

LOPEZ: “Show Yourself” took months and months of writing. The first version of it was, I think, six-and-a-half minutes long. It’s an epic number that needed to come down, so we shaved away at it, but there was also a lot of rewriting and rethinking. It had several different endings. It was just a real intense labor of love.

ANDERSON-LOPEZ: The biggest challenge in all of these—it was this way for Winnie the Pooh and for Frozen—is that you write songs sometimes, and then the story changes. No matter how much you love those songs, they fall on the floor, and that’s a moment where Bobby and I have now learned to turn to each other and say, “Well, that’s a shame. We loved that song, but now we get to write a new song,” which we love to do. We’ve had to reframe those moments that a song gets cut, into “We get to do another thing that we love.” That has really made life much better. We don’t look at them as failures; we look at them as growth.

DEADLINE: What about your work on this film makes you the most proud?

ANDERSON-LOPEZ: The thing that we feel most grateful for is being able to work with this incredible studio. We get to write these songs in Brooklyn and send them out there, and then some of the best artists in the whole world breathe life into them, and make them so magical on the screen. I think more than ever, we feel gratitude that our career has put us in this position. So, that’s the thing we’re most proud of—getting to work with these amazing artists, and hopefully give them as much credit as possible for what they do.