Triangle, the latest record from Norwegian singer Susanna Wallumrød represents the biggest stylistic shift of her career. Whilst she's previously incorporated lots of different musical influences into her work, the overall aesthetic has tended towards quiet, almost delicate tones. In contrast Triangle embraces far more abrasive sounds as well as drawing in influence from noise genres. "I think of the albums as one thing and the live concerts to be a little bit different," Susanna explains over the phone. "So the very subtle moods on the albums have evolved into something louder over the years. Maybe that's also why this album has turned out the way it has? I definitely think the different projects, collaborations and albums that I've done have led up to this. I don't think I could have made this album earlier."

If there's one element of Susanna's career which appears to have had the greatest influence on her new album it's Meshes of Voice, her collaboration with Jenny Hval which was released in 2014. "The whole collaboration with Jenny has been very important to me," Susanna explains. "Afterwards when I continued to write music and lyrics it was like the next chapter somehow."

That next chapter started not long after the Meshes of Voice collaboration. In 2010 (one year after Meshes of Voice was written and recorded) Susanna began to write what would become Triangle, gathering together the first set of lyrics and musical ideas. "I had these very concentrated periods where I'd been writing songs and working with it. I very much wanted to just take my time to write and write and write." Not content to just limit herself to a simple ten-track album, Triangle has evolved into a 22-track odyssey. "I wanted to see how far I could go with this," Susanna continues. "I knew quite early on that this was going to be a massive album, but I didn't know exactly how [massive] it was going to be - that happened when I started to record."

Recording started in 2015 whilst Susanna was in Los Angeles. She confined herself to what she described as a "wooden hut in a park". Removed from distractions Susanna was able to just focus on creating music, and get a decent start on the record. After an initial burst of work in LA, she took what she'd made back to Oslo where she continued to work on it on and off over the coming months.

"I think it was necessary for all that music," Susanna responds when asked about writing and recording the album over such an extended period. "I wanted to be totally free to make different types of songs and not limit myself to just a certain style. But that could of course have been very bad." What prevented the album from being a collection of disparate ideas was the fact that Susanna made sure to work on groups of recordings rather than just an individual track here or there. "It meant that I could pick things up and work on [a song] and then I could close the project and pick up a new song and work on [that]. I got this connection between the arrangements and how I wanted to present the songs."

As a result of this process Susanna also ended up producing the album alone. Whilst she's had production credits on many of her previous albums, they've usually all been in collaboration with another artist - this was to be her first time going solo. "It was very frustrating," she admits. "I've always been co-producing and I know [exactly] what I want, but I always find out [something else] in the dialogue with other people. So to not have that dialogue was incredibly hard. I got so tired of my own thoughts and of my own perspectives that I had to talk with [other] people to just let my frustration out and also have some advice during the process." Susanna turned to other musicians who contributed to the album's instrumentals to work on the arrangements with her and also signed up guest producers to work on a few of the album's tracks alongside her.

Whilst Triangle being self-produced was partly due to the lengthy process Susanna had taken I also wondered if it might also be because of the personal nature of the album's subject matter - spirituality. Did Susanna feel the need to retain personal control over the ideas and themes she wanted to explore?

"Yeah, that may be," she responds. "I definitely thought about that during the process, that it felt like I could do stuff that I wouldn't do if anyone else was there. Which is a weird thing for an album you're going to put out and let other people hear. But it was very liberating to just do it myself and kind of steer the ship."

Susanna was brought up in a Christian family and has been a member of various churches from a young age - an experience she describes as alienating. "There wasn't room for other thoughts," she explains. As a teenager Susanna made an attempt to break free from this and examine what her beliefs truly were. In a sense Triangle, with its exploration of spirituality is an extension of that journey. "I wanted to dig in to the themes of spirituality a little deeper and go further into other areas that are a little bit scary to explore what we believe in, what is belief and all these things they can lead to." And this wasn't just limited to religion. "People can be convinced by other things as well, not only religion," Susanna continues. "We still have a society that finds it very challenging every time someone starts to ask questions about why things are a certain way, or why we do things a certain way. We don't want to have questions or doubt."

Triangle really exemplifies Susanna's skill as an artist and songwriter. Even at 22-tracks the album feels concise and consistent, with one track flowing into the next with ease. Yet despite this (and several older records of original material) Susanna is often considered a 'covers artist'. Whilst it's true that Susanna's early career, particularly as Susanna and the Magical Orchestra, saw her releasing albums filled with covers this hasn't been her primary focus for many years. "I wanted to bring my own songwriting to the same level of recognition," Susanna says. "It's weird because people think you do one or the other and not both. So every time that I've released an album with my own songs people are like, 'oh yeah she's stopped with the covers' and then there's a new album of covers and they say 'oh she's back with covers again?' Why can't I just do both?"

Susanna's interest in covers came out of an interest in jazz. "I had been doing jazz and jazz standards," she explains. "I was very interested in that type of music and how they're so good at finding their own voice and their own interpretations of songs - taking [songs from musical] into a smoky club and playing them on saxophone. There's a tradition there which is very inspiring I think." For Susanna performing covers is just part of being a singer. She cites Nina Simone as a particular influence, noting her ability to adopt other people's songs both traditional and contemporary and make them wholly her own.

That sense of reinterpreting a song or finding something new to say in it is what drives Susanna with her music. "I've always thought of it as the same thing, doing an interpretation, or version of a song and writing my own stuff. Here in Norway we have a lot of radio shows where people get invited to do cover songs of other people's work. And I don't say that it's never a good version or a nice version, but it feels like a gimmick. It feels very empty and I am not a part of that - it's not why I do other people's songs."

In fact, Susanna's reinterpretations of songs are often so far removed from the original track that they take on new lives - sitting comfortably on a record of other covers and original material as though they had been written for that purpose. She recalls a moment though when one reinterpretation became inseparable from the original, however. Susanna was collaborating with baroque harpist Giovanna Pessi. "We were usually playing Henry Purcell, Leonard Cohen and my own songs," she says, "but after a while I wanted to add an AC/DC song. It's just so nice to play with baroque harp and old string instruments." The song in question was 'It's a Long Way to the Top', which Susanna recorded for Melody Mountain.

"We played at this chamber music festival in Bratislava, in a huge cathedral in the town. Sometimes I don't say anything about the song, but at that particular concert I made a joke saying like, 'I don't think AC/DC has ever been played in this cathedral before'. I played the same festival a couple of years later and found it was a catholic cathedral and after our concert they had started to review all the material that was going to be played there. So the chamber festival really has some issues with the cathedral now. I don't think they would have noticed if I hadn't said so, but because I actually said something, it's a thing now unfortunately."

Triangle by Susanna is out now