It's enough of a challenge to capture a life like Nelson Mandela's in a 146-minute film, but how do you use music to reflect such an extraordinary man? That is the challenge that faced composer Alex Heffes on Justin Chadwick's "Mandela: A Long Walk to Freedom," and his compositions have since earned him a Golden Globe nomination for Best Original Score.

Heffes, who had worked with Chadwick before, was advised of the feature early on. "I originally spoke to Justin before filming even started – what he wanted to achieve in terms of the movie and how he was thinking about it," Heffes says. "He was trying to focus on the family story and how his public life impacted his personal life."

However, Heffes did not start composing until Spring 2013. "The actual writing was quite quick but I went to South Africa to record," he says. "It was rather unusual – a long period of gestation, a quick turn around and a long period of post-production."

The film required a blend of dramatic personal themes, traditional African-styled music and a delicate balancing of accentuating what we see on screen without taking away from the performances. And while Heffes cites complementing the performances of Idris Elba and Naomie Harris as "the start" of his work and what he could never get away from, it was his journey to the great continent that was particularly unique.

But Heffes "was conscious of not wanting to make the work into a travelogue," he says. "There is a lot of authentic African music in the street scenes. I felt that was well-captured already in the film. I wanted to concentrate on the family and personal struggle. That's universal."

There was a layer of African/South African music that he wanted to integrate into the score and he sought out authentic musicians to play the instruments. "We wanted some percussion from the Eastern Cape where Mandela was born and we brought in people who could do correct infractions," he explains

In this respect, it was the people who were more important than the instruments. There were percussion instruments in the score he had never used before. And while a lot of the instruments  were recognizable, the way they are played on the score is very different. "Seeing how South African musicians would react to the music and put their own stamp on it was fascinating," he says.

Even throughout this process, however, Heffes was also conscious about making sure the film spoke with "melodic integrity." It's one thing to have indigenous flare but another to speak the language of film music, and to tie the two concepts together.

Composing involved more than sitting alone in a room writing music and traveling to South Africa to record it, however. It also involved collaborating with the film's sound artists and film editor. "I first saw a cut in late February 2013," Heffes says. "It was a first cut and it was very, very powerful. It was longer than the cut is now but was structured pretty much the same way."

The first person on the film Heffes would usually work with was of course director Chadwick, who Heffes describes as "very very open. He hires people that he trusts and he gently steers in the direction he wants it to go. He has an openness and willingness to collaborate and a very clear vision."

Something that was quite unusual as the film was sculpted in post-production is that a few scenes were actually re-cut for music. Typically picture edit is locked by the time a composer comes around to it. When he felt he had a perfect cue that needed some extension, "Justin would literally hear the cue and he'd phone up the editor and ask to add ten seconds," Heffes says.

The principle challenge, however, was "the responsibility of telling such an important story and remaining true to it and remaining as honest as I could," Heffes explains. "I think the story is so dramatic that if you hadn't seen it in real life you wouldn't believe it. It needed to be respectful to the people involved and true to the movie.

"This is one of the most complicated narrative stories because the time span of the film covers such a long period. Just navigating that – it had to start off in the 1930s and morph through the ‘40s and ‘50s palette to get more present day. I consciously tried to evolve the music over time. Audiences may not be aware of it but subliminally my hope is that it conveys that."

And now, the film comes at an extraordinary time. Mandela's daughters were at the London premiere where it was announced at the end that the great freedom fighter had passed away, the whole of Heffes' and the filmmakers' work taking on a whole new shape. "The lens of scrutiny is very much focused," he says.

"Mandela: Long Walk to Freedom" is now playing in theaters.