Frozen is the most successful animated film of all time. Take a moment to let that sink in. Since its release in November 2013, Frozen has surpassed two decades’ worth of hits by Pixar, DreamWorks & Disney, and grossed over $1.2 billion in worldwide box office revenue. This accomplishment also makes it the fifth highest-grossing film in cinema history. The achievements of Frozen’s soundtrack are perhaps more remarkable still. The album has topped the Billboard charts for 13 weeks and counting, the best performance for a film soundtrack since Titanic in 1998. ‘Let It Go’, the film’s centrepiece anthem, won the Oscar for Best Original Song and has racked up more than a quarter of a billion views on YouTube. These are mind-blowing statistics. But more remarkable still is the story behind the film’s creation, and - in particular - the role of the aforementioned song in the film’s protracted development. A power-ballad delivered by singer Idina Menzel, the show-stopper’s stirring arrival midway through Frozen signals more than just the end of Act One. It represents a turning point in the film’s 70-year journey to the silver screen, a milestone in CGI animation technology, a tribute to a late Broadway icon, and - some say - the start of a second Disney renaissance.

Frozen Heart Walt Disney himself saw the cinematic potential of The Snow Queen, the Hans Christian Anderson fairy tale on which Frozen is based. As early as 1943, Disney was in talks with Samuel Goldwyn regarding a collaborative film about the life and works of the beloved Danish author. Concept art for the Andersen biopic His plans fell through, however, running into the same thorny issue that would scupper Disney’s adaptation efforts for the next seven decades: the titular character herself. The Snow Queen has neither motive nor backstory, and does not even feature in the story’s climax; she is a two-dimensional villain in a largely symbolic story. Despite her stunning appearance - “fair and beautiful, and dressed in garments of white gauze, which looked like millions of starry snow-flakes linked together” - this literary version of the Snow Queen simply did not lend herself to the silver screen. One of Anderson’s other characters proved more forthcoming. The release of The Little Mermaid in 1989 heralded the start of the second golden age of Disney animation; the so-called Disney Renaissance. Collaboration with Broadway talent Howard Ashman and Alan Menken revitalised the lagging Disney brand, and Anderson’s Mermaid was quickly joined by musical classics such as Beauty and the Beast and Aladdin. The Snow Queen, by Elena Ringo Throughout this period, interest in an adaptation of The Snow Queen remained high. Disney’s then-CEO Michael Eisner was a particular fan of the project. In 2003, towards the end of his tenure at the company, he met with the company’s feature animation team to discuss their upcoming slate of movies. James B. Stewart recalls the executive’s enthusiasm in his book Disneywar. “The Snow Queen is a terrible bitch,” explained creative vice president Mary Jane Ruggels to Eisner. “When her suitors try to melt her heart, the Snow Queen freezes them. Then along comes this regular guy.” “This is perfect,” Eisner exclaimed, apparently unaware that thin characterisation was the very issue that had plagued the project thus far. Snow Queen concept art from the early 2000s “The regular guy goes up there,” Ruggels continued, “he starts to unfreeze her… she melts.” “It’s great,” declared a triumphant Eisner. “Finally. We’ve had twenty meetings on this.” Ruggels promised to have a full treatment for the film ready in just two weeks. Unsurprisingly - and perhaps thankfully - this incarnation of The Snow Queen didn’t make it past the drawing board, and film was once again put on indefinite hiatus. Development hell continued to plague the project, and it passed through the hands of dozens of Disney veterans including animation legend Glen Keane (who went on to produce Tangled) and the Brizzi brothers (The Hunchback of Notre Dame, Fantasia 2000). No-one, it seemed, could break the ice that had enshrouded the project.

For The First Time in Forever Fast-forward to 2012, and the project was finally beginning to show signs of life. Chris Buck, Peter Del Vecho, and Jennifer Lee Frozen had been announced as a computer-animated feature, with Chris Buck and Jennifer Lee at the helm at co-directors, Peter Del Vecho as producer, and Pixar’s John Lasseter overseeing the project. Buck was a Disney veteran, having co-directed Tarzan and Surf’s Up, but for Lee - screenwriter of Wreck-It Ralph - the film marked her first time in the director’s chair. Incidentally, this also made Frozen the first full-length animated Disney film to have a female director. To pen the film’s musical numbers, Disney once again turned to emerging Broadway talent in the form of Bobby Lopez, best known for his work on Avenue Q and The Book of Mormon, and his wife Kristen Anderson-Lopez, famous for her work on 2011’s Winnie the Pooh. With the production team based in Los Angeles, collaboration with the New York City-based songwriters necessitated two-hour-long videoconferences every single day. Kristen Anderson-Lopez and Bobby Lopez And still, the Snow Queen herself proved troublesome. The team had already added an exciting new dynamic to the tale by making protagonist ‘Anna’ and Snow Queen ‘Elsa’ sisters, but there was still a way to go before the characters would feel truly compelling. “With Elsa, we were still going on the villain journey,” explained Lee. “It was killing me to try to figure out how to make that work, and then redeem her. And have a love story. I was dying!” Amusingly, none of the creative team can remember who originally came up with the sibling idea; it simply materialised during a group brainstorming session. There is, however, no doubt about the origin of the next breakthrough. “You have to understand why every character does what they do, whether they’re the bad guys or the good guys. You have to understand their philosophy, even if you don’t believe in it.” - John Lasseter When Bobby Lopez and Kristen Anderson-Lopez delivered their first demo of ‘Let It Go’ (which had been provisionally titled ‘Elsa’s Badass Song’), the film’s true story line suddenly revealed itself. “The minute we heard the song the first time, I knew that I had to rewrite the whole movie,” said Lee. The song delivered precisely what the writers needed: a compelling motivation for the Snow Queen. Gone was the simplistic villain, replaced instead by the complex and sympathetic character of Elsa, a girl struggling to come to terms with her gifts and glorying in a rush of reckless self-empowerment. Elsa character sketches, by Jin Kim Incredibly, the Lopezes had written the song from scratch in a single day, an achievement made yet more remarkable by the fact that the final version of the song matches their first demo recording word-for-word and note-for-note. Pixar creative chief John Lasseter was reportedly so taken with the track that he played it every day in his car for nine months straight. Musically, the pair had been guided by the casting of Tony Award-winning stage icon Idina Menzel, famous for her performance of the power ballad ‘Defying Gravity’ in Wicked and for her starring role in Glee. In composing the song, the actress’s three-octave vocal range was taken into consideration, and finding singers capable of matching this in their native tongue would later prove to be a major challenge to the translation and localisation project. Anna character sketches, by Jin Kim With “Elsa’s Badass Song” realised, all the pieces began to fall into place. The writers had a pair of highly compelling protagonists, and the central thrust of Frozen’s narrative was finally taking shape. Production continued with a renewed vigour, and a total of 25 songs were eventually written for Frozen, of which two-thirds were discarded during the film’s development. Publicly, the studio was reluctant to market Frozen as a musical, fearing that certain audiences would be put off. Privately however, the production team expressed a level of enthusiasm which betrayed their convictions that the film’s songs would one day be “as classic as those in Beauty and the Beast”, the Disney high-water mark from 22 years ago.

Do You Want to Build a Snowman? The team’s triumph over decades of creative inertia did not occur until November 2012, less than a year before the film’s slated release date. With Frozen’s script still evolving, the production team were now faced with a challenge yet more daunting: actually making the entire film in less than a year. Other films had been completed on a tighter schedule - Toy Story 2 was famously produced by Pixar in just 9 months - but few of these were as technically demanding as Frozen was shaping up to be. Concept art by James Finch, inspired by the Norwegian village of Balestrand Art director Mike Giaimo had been developing the film’s visual style whilst the script was still evolving. Animators and artists had taken research trips to Norway, seeking a Scandinavian influence for the fictional kingdom of Arendelle. The spectacle of the Norwegian fjords guided the design aesthetic of Frozen’s winter landscape, whilst the country’s medieval stave churches and rosemåling folk art served as inspiration for the film’s architecture and costumes. “We wanted to create an intimate world with an enchanting and dynamic setting that would be immediately identifiable for generations to come,” Giaimo explained. “Norway offered a cultural backdrop we’d never explored before and we thought, ‘Wouldn’t it be great to blend its dramatic natural environment, architecture and folk costume aesthetic?’ It feels like a world from a classic Disney film, but it’s completely new.” Arendelle in deep snow, by James Finch Having settled on Frozen’s art direction, the animators and special-effects artists soon discovered that their wintry locale presented a new problem: snow. In short, it had never before been convincingly animated. Given John Lasseter’s famous insistence on ‘truth in materials,’ even in fantasy settings, animating the film required extensive research. To give them reference material for the scenes of characters interacting with heavy snow, animators were sent on field trips to experience running and falling in deep snow in a variety of attire. In a true testament to their commitment, both male and female artists traversed heavy snowdrifts whilst wearing dresses. “As much as a snowy, icy backdrop offers this beautiful blank slate where anything is possible, it’s really tough to get it right - to make it believable, and then take it somewhere magical.” - Chris Buck So demanding were many of the film’s scenes that their production entailed the development of entirely new technologies. Chief among these was Matterhorn, a snow simulator developed in collaboration with UCLA physicists. An algorithm based on the material point method, it harnessed engineering principles to capture the unique ‘sticky’ quality of snow, and allowed complex interactions between characters and snow to be realistically animated. In addition to Matterhorn, the film necessitated the invention of dozens of new animation tools. These included Tonic, a program used to sculpt characters’ hair as procedural volumes - Elsa’s hair was crafted from 420,000 individual strands, dwarfing Rapunzel’s 27,000 in Tangled - and Flourish, which allowed artists to capture the movement and stretch of different textiles used in characters’ clothing. Elsa embraces her powers on the mountain Fittingly, the ‘Let It Go’ sequence once again proved pivotal. As one of the most technically-complex scenes in the entire film, for many in the production team it came to represent the myriad of challenges they had faced - and overcome - in animating Frozen. The musical sequence called for Elsa, newly-exiled to the mountains overlooking Arendelle, to conjure herself a palace. Constructing her new home from the ice and snow of her surroundings, she would embrace her powers and transform herself into a queen. The scene was crucial; it had to do justice to the Lopezes’ breakthrough song, and also pack a visceral punch worthy of its significance to Frozen’s story. Ice palace concept art, by David Womersley The architecture of her palace was inspired by an idea of John Lasseter’s; he suggested that Elsa’s new home be modelled after the elegant, hexagonal symmetry of a single snowflake. Its every aspect would celebrate this simple geometric motif, right down to its construction, which would follow the same branching and plating process by which real snowflakes form. Establishing the visual style of the sequence required a field trip to an ice hotel in Quebec. “We brought back all of this wonderful detail,” explains director Buck, commenting on the unique optics of the building. “The way the light refracts, the colours - so many things were inspired by all of this research.” In animating the shot, fifty effects artists and lighting artists worked together on the technology required to execute the sequence. Such was its complexity, the scene took 4,000 computers over 30 hours to render each and every frame. “That’s why that scene is one of my favourites,” explains director Lee. “It really represents the journey all of us took on this movie.” Head of story Paul Briggs summed up the team’s attitude as production on Frozen drew to a close. Despite the tremendous technical challenges and constant pressure to finish the film, the prevailing mood was one of cautious optimism. “I believe in the film,” he explained. “When you’re working on something that’s really emotional and powerful, it’s inspiring. You get it done because you know it’s going to be great.”