All the new lyrics are about the natural world, with each song evoking a different element of nature.
In the NORTH Project MaJiKer - Paris-based producer, composer and vocalist Matthew Ker - takes traditional tunes, engages some of Europe's most adventurous vocalists and gives the songs a new, English-language meaning.
Now he has released them online in aid of Naturskyddsföreningen, the Swedish Society for Nature Conservation, with all profits from sales and streaming donated to help spread knowledge, chart threats and propose solutions to the world's environmental challenges.
I asked him about that four-year journey - did it start from a desire to make an environmental statement? "To be honest, I was not massively into nature to begin with", he admits, "although living in Paris, as I get older I do find I need to escape to the countryside every week or so.
"It started with these lovely melodies. Each of them is a folk tune introduced to me by someone who has a personal or emotional connection to it. The language - whether Icelandic, Swedish or Norwegian - is so much part of that sound-world. I tried to capture the sound of the lyrics whilst writing in English."
A folkloric history of landscape
"All the new lyrics are about the natural world, with each song evoking a different element of nature. I was imagining what these natural features would sing if they could tell us of their past; a sort of folkloric history of the landscape itself."
So the English lyrics are not based on the meaning of the original words, but on their sounds? "Exactly, and it was the search for lyrical content that made me investigate the natural landscapes in great detail."
The songs cover a range of natural subjects including rivers, pinewoods, birds, even soil, he adds. "Re-imagining the lyrics enabled me to inject life and zest into the potentially flat theme of soil by depicting all the creatures that feverishly dig beneath the surface."
As well as being a successful producer - with French experimental pop singer Camille's double-platinum Le Fil heading up his CV - MaJiKer is a composer and vocalist with a unique knack of getting other performers to push their boundaries.
His collaborators on NORTH include Mercury-nominated folk star Sam Lee, jazz-soul diva China Moses, female punk choir Gaggle, Swedish singer-songwriter Jennie Abrahamson, and British vocal ensemble juice.
I asked juice's Kerry Andrew to explain how her trio got involved. "We were already a fan of MajiKer's work with Camille. We loved how he created our song Rocks of Ritual by coming up with new English text that sounded as close to the Swedish original as possible, but with a totally new meaning!"
Landscape and nature are deeply-rooted in Nordic culture
I wondered if Rocks of Ritual - with both a changed text and a radical musical treatment - would upset some folk purists? "We know from our gigs over the years that folk audiences are very open minded. They appreciate a contemporary twist. At the same time, we're treating these tunes with the utmost respect.
"juice all have backgrounds in contemporary classical music but we sang at the Tampere [Finland] Vocal Music Festival in 2007 and 2009 and got a strong sense of how embedded folk music is there. The landscape and nature are still a deeply-rooted part of Nordic culture."
As the project started to take shape, MaJiker felt there was still something that hadn't yet clicked into place. It was the realisation that at the project's heart is a message about the beauty of nature and a plea to support its conservation.
"And so the final piece of the jigsaw was the decision to work outside the label system, forget the idea of a CD and work with Naturskyddsföreningen to release the album online, to raise funds and spread the word."
So where next? "This is just the start. The project website is inviting people to upload their own cover versions so that these songs and their messages evolve and have a life of their own.
"And we're doing gigs, hopefully culminating in a show here in Paris at next year's Climate Summit. I wonder how many of the world's leaders will come along."