Behind the music of 'Frozen 2': Stars and songwriters talk Elsa's new hit and Kristoff's show-stealing '80s rock ballad

Talk about a tough act to follow. The folks behind Frozen 2, Disney's hotly anticipated sequel to the 2013 box-office/cultural phenomenon Frozen, not only had to deliver in the story department, but they also had to craft a soundtrack that could follow the ubiquitous tunes of its predecessor. Led by the unescapable smash single "Let It Go," the original Frozen soundtrack was certified triple platinum and won both an Oscar and a Grammy.

All the pressure fell upon the film's award-winning songwriters, the husband and wife team of Bobby Lopez and Kristin Anderson-Lopez. And, as the cast insists, the Lopezes delivered.

"We're lucky, because we have the Lopezes, who are these incredible songwriters, and a lot was on their shoulders," Idina Menzel, who plays Elsa, told Yahoo Entertainment (watch above). "They've gotten to know us as singers, and as people, so they start to write with us in mind."

"Bobby and Kristen can't write a bad song, so that was a plus going in," said Jonathan Groff (Kristoff), who was paired with Josh Gad (Olaf).

Kristen Bell, who voices Elsa's sister, Anna, said the songwriters know the stars' "sweet spots."

"They know how to write in the notes that we can hit really well. So both of our songs lead up to the notes that we can hit really well."

Bell's marquee track is "The Next Right Thing," while the Menzel-crooned power anthem "Into the Unknown" is already being called the new "Let It Go."

"The first time, we had great storytellers who inspired us and gave us characters who had big feelings and big decisions to make, and that's where the songs spring out of," explained Anderson-Lopez. "And we had the same thing the second time around."

With Bobby in front of a piano and Kristin singing, the pair demonstrated how "Into the Unknown" evolved over the course of its writing as the pair attempted to land on more "mysterious" chords that would tease the discovery of Elsa's mystical powers in the film.

Speaking of discoveries, in Frozen 2 we find out that our old friend Kristoff, the ice salesman who won Anna's heart in the first film, can really sing — and his '80s-inspired rock ballad "Lost in the Woods," complete with visuals straight out of a Bryan Adams or Richard Marx video, is one of the most talked-about scenes in the film.

"With a character like Kristoff, you haven't gotten access to his emotional mind," explained writer-director-Disney Animation chief Jennifer Lee. "And to imagine that his emotional mind when you're allowed inside is a giant big '80s ballad was just too delicious."

Added Groff: "Bobby and Kristin sent me the song and they said, 'It feels like Kristoff is this straight dude trying to express himself. So of course it lands in the world of like '80s slow-jam rock ballads because a lot of straight dudes can relate to that."

Frozen 2 is now in theaters.

Kristen Bell and Idina Menzel reveal that their kids are not fans of their Frozen singing:

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