After "The Beach," Boyle did a pair of television movies ("Strumpet" and "Vacuuming Completely Nude in Paradise") to test out the digital technology that would define the look of his next theatrical feature, revisionist zombie epic "28 Days Later." He didn't use Underworld for any of these projects, or the one that followed after, a lovely little bedtime story of a movie called "Millions." The band was recruited, however, for 2007's ambitious sci-fi project "Sunshine," about a team of astronauts tasked with "restarting" the sun. Underworld took on an additional role with "Sunshine," serving as co-composers alongside John Murphy.

Underworld had just finished the score for what would ultimately be director Anthony Minghella's last feature, "Breaking and Entering," when Boyle came calling. "Danny tells us that he knew this and he wanted to talk to us about 'Sunshine' a lot earlier," Smith said. "We came to it and we weren't able to invest a lot of time, we had a few weeks to do it. I really enjoyed it. When Danny showed us the first cut with the temp, my partner Karl and I thought it was fantastically exciting and we launched into the composition for that actually jamming to the picture and assembling a kind of alphabet of ideas and sounds and harsh states. Then we passed this stuff over to John, who had moved to L.A."

Those "harsh states" include sound effects and cues that seemingly blur the line between sound design and score, something that Smith is hesitant to take full responsibility for. "I think it would be unfair if I was to give the impression that all the crazy sounds was us, but the noise and the crazy visceral feelings were certainly things we were drawn to and spent some time on."

Underworld also got to contribute a new song called "Peggy Sussed" – a propulsive number that plays over the end credits and serves to effectively shred what's left of the audience's nerves after the film's harrowing finale. "That's the thing with Danny – he has ideas but he's always looking to be surprised. And he'll say so himself. The other day someone asked, 'How do you know when something's working?' And the way to know when something's not working is the music and the images seem separate. You know in his work, those things absolutely combine and you go, 'That's perfect.' That seems to be the case with 'Peggy Sussed.'"

Frankenstein Benedict Cumberbatch Jonny Lee Miller
"Frankenstein" & Olympics
For Boyle's next two features – "Slumdog Millionaire" and "127 Hours" – he would rely primarily on noted Bollywood composer A.R. Rahman for the music. But that doesn't mean that he didn't collaborate with Underworld on two high-profile, non-movie projects. In 2011, Underworld scored Boyle's production of "Frankenstein" for the Royal National Theatre. And last year the duo contributed music to the Summer Olympic Games, held in London, which were creatively overseen by Boyle.

Smith described their work on "Frankenstein" as "absolutely extraordinary," adding "I've never worked so closely inside theater. We got deep inside." And it wasn't just the score they were responsible for, either. "Danny asked us to take care of all aspects of the sound – everything from the sound system to the sound of the actors, to the underscore and the score," Smith said. Even though that amount of work seems positively daunting, he was unphased: "It was the most fun I've ever had. It was a piece that evolved alongside the rehearsals with the actors, evolved in the space, and was such a huge pleasure and exciting. Very exciting."

The Olympics, on the other hand, was a different beast altogether, one that Smith described like you would describe some kind of large engine or a civics engineering project. "Most people involved felt a huge amount of pressure," Smtih said. "There were thousands of people. It nearly broke people." Even Smith, who had worked with Boyle for decades, felt a little iffy. "It was a big ask. I suppose, it was knowing that Danny had asked, that made me feel like I could do it. It was the type of thing that made me think, 'I don't know if I can do it.' But Danny asked, so I'm gonna have to."

Ultimately, though, it proved rewarding. "It was an extraordinary journey with a tremendous result. Very inspiring. Working with the volunteer drummers, particularly, was a life-affirming experience. We could talk for hours just on the opening ceremony."

Rosario Dawson, Trance

For Boyle's post-Olympics film "Trance," he once again turned to Underworld to provide the music, although it's a somewhat different scenario this time around as it's the first complete score Smith had worked on for Boyle and the first one he had completed without his longtime partner Hyde (who was working on his debut solo album). The film proved difficult in other ways, too.

"It was challenging because I came to the project quite late on. They had shot the movie, then did a very rough assembly, then parked it to work on the opening ceremonies for the Olympics, and then picked it up again. So they took a hiatus, which was very unusual for film," Smith explained. Not that there was any doubt that he would do the project. "It was a yes for me, because I knew working with Danny was going to be a thrilling experience again. For a composer, a film like that about a puzzle is a puzzle and where the score needs to drive things along but also explore what's going on, the changing nature of what's going on inside the actors' heads. It was challenging, but Danny was always there to guide you."

One of the highlights of the movie is a song that Smith wrote for British pop star Emilie Sande called "Here It Comes," and we asked how it came together. "I had been working on the score for a while and Danny was in the studio and what became apparent was that we needed a theme to counterpoint the darkness and anger and the things going on in peoples' heads, and something to suggest a love seeded between two of the characters," Smith says of the song's practical origins. Still, the nugget of the song went back even further. "I had a part of an idea, a piece I had originally started whistling on a balcony in Mexico City in 2008. As is the case with most writing, sometimes you pick up ideas years later. And it worked very well for the points we needed in the film in its instrumental nature, but I felt that it could be developed and it would be fantastic if we could get Emilie." In fact, it had been Boyle who had brought Sande and Smith together once before. "I had worked with her on the opening ceremony and I just felt that she could voice, from that female point of view, something that could take it to the next level. She's got an extraordinary voice and she's a great songwriter."

Much like "Born Slippy," the new song adds a lot of poppy bounce to a movie that is largely defined by violence and darkness. Again, Smith throws it back to Boyle. "Danny always talks about, when people ask him about his films, the fact that he feels that in all of his films there is a character who faces huge odds, overcomes them, and there is a kind of redemptive nature and a positive feeling to what happens at the end of the film. And I think he's probably right. This piece was very appropriate for that." It's true: Underworld and Danny Boyle make beautiful music together, and "Trance" is just the latest example.

"Trance" is now playing across the country.