The Knife have already proved themselves to be rather more than the average electro duo; from the uncanny beauty of their 2005 odyssey Silent Shout to their rejection of industry awards and penchant for wearing masks in public, the Swedish siblings Olof Dreijer and Karin Dreijer Andersson (a.k.a. Fever Ray) have been keen to push the boundaries of popular music.

It was therefore only a mild surprise to discover that the pair’s latest project was writing the music for an opera about Charles Darwin, to be staged by Danish theatre company Hotel Pro Forma. In Tomorrow, in a Year, which premiered in Copenhagen last September, an opera singer, a pop singer and an actor perform The Knife’s music and represent Darwin, time and nature on stage. Six dancers form the raw material of life.”

While the opera now tours various European cities, The Knife have released an augmented version of the score on their own Rabid Records, parts of which were composed in collaboration with Mt. Sims and Planningtorock. Olof Dreijer talks to FACT about the evolution of this unusual project and their new found joy in collaborating with others.

You were initially contacted by Hotel Pro Forma about doing the music for the opera in early 2008. What was it about the project and the concept that attracted you?

“Initially it was more of a performance with music and dance that they wanted to call an opera, and basically focus more on the meaning of the word ‘opera’ meaning just a piece of work. And they wanted to focus on Darwin with a focus on biology and geology, to give an abstract feeling of what evolution could have been like.”

That sounds like quite a daunting proposition to me. How did you approach it and what was the starting point in terms of working on it?

“All the collaborators – us, the lighting designer, the choreographer, and so on – were all given a literature list and lots of notes from Darwin, so there was a lot to read in the beginning. It was really exciting: we started out by making small musical exercises on the theories we read about; it was really quite a direct translation from theory to music. In fact almost every musical choice throughout the whole process has been very conceptual: each sound has come from a theory. That made working on it really difficult but really fun too. I think it’s been really exciting to take his notes, his theory and work with them.”

When did Planningtorock and Mt. Sims get involved in the project?

“We thought quite early on that it would be good to collaborate with them – we knew each other already and I had been thinking it would be great to do something together, so it was a great opportunity to try this. We also thought it was too big a theme to portray with just two brains. I think one way to illustrate this huge diversity you get when you read Darwin was to have different styles and different goals, so that was one reason why we wanted to have them on board. One good thing about working with Mt. Sims, for example, was to do with the lyrics. We were asked to write the libretto in this very Victorian language and it was very difficult to go about that: to avoid making the lyrics too pretentious and find an emotional value in them, a value that was interesting. Mt. Sims’ way of writing was a bit more classical poetry whereas Karin’s is a bit more abstract-contemporary. They also moved in between these areas, but that combination of their different lyric styles was very good and something we wanted to go for.

“We also wanted to have very diverse sounds: one way to approach the word ‘opera’ was to be very creative with the orchestration, something Planningtorock had great experience of, so she and I went to Iceland to record with this percussionist who had a very strange and exciting collection of instruments. We would give him recordings of animals that I had done in the Amazon and let him interpret these recordings and come up with sounds that you didn’t really know if they were animal sounds or electronic sounds or acoustic sounds and try and blur out these separations. So yeah, these different things have been very exciting.”

Was it difficult for you to write for all the different vocalists?

“Yeah, that was really difficult. There was one opera singer [Kristina Wahlin Momme], one pop singer [Jonathan Johansson] and one actress [Laerke Winther] and they had completely different experience of singing, and we had to come up with vocal lines that would fit and we had never written music for any other singer before, so that was really difficult, but also really exciting. We really studied the opera singer a lot: what she was able to do, what sounded good. I had never been to an opera, so we went to one and tried to find different, exciting ways to work with this format. We actually studied more contemporary experimental vocal composers than classical opera to find ways to work with the voice as an instrument and come up with something that would fit into the collage of sound.”

The opera itself lasts 80 minutes, but the album’s 92: what’s different between the two?

“The main difference is onstage all the vocals are sung by these three singers, and on the record we recorded one verse each with Mt. Sims and Planningtorock and Karin to kind of point out how this piece can be sung by different singers in the future: it’s a piece that can appear in different versions. Then we kind of worked more on the production, more exciting vocal sounds, and some of the songs are longer on the record as well, because they were cut in the performed version. But apart from this it’s pretty much the same, although in the performed version it’s surround sound here and there and on the record it’s stereo.”