Björn Ulvaeus laughs when I ask about his early experiences in the music business in the 1960s. “Pre-Abba, even?” Back in those distant days, before the Abba man became a quarter of Sweden’s most successful overseas force since the Vikings, Ulvaeus was in a winsome folk-pop band called the Hootenanny Singers.

They had their first hit in 1963, the sexily titled “Jag Väntar Vid Min Mila” (“I’m Waiting by My Charcoal Kiln”) at the same time as The Beatles’ first hit in Sweden. Ulvaeus remembers watching the Liverpudlians on tour with envy.

“I thought to myself, bloody hell, I have a hit now and it’s in a folk group but I would love to be a pop group,” he says. The seeds of Abba were planted in the shade of Beatlemania. “Deep in our hearts, what we wanted to do was pop music in English,” he says. “That’s how Abba started really.”

Fifty years later, Sweden is a pop powerhouse. In 2011 the nation of 9.5m produced music exports worth more than $150m (according to Swedish industry estimates) – the largest per capita in the world. Now the rest of the Nordic region is catching up.

Indie bands spill out of Reykjavik. Heavy metallers headbang in Finland. Danish singer-songwriter Agnes Obel tops album charts across Europe. Oslo’s answer to “Gangnam Style”, Ylvis’s “The Fox (What Does the Fox Say?)”, is a YouTube hit.

Meanwhile the Swedish machine forges on with Avicii, the DJ conquering the world with his unholy brew of electronic dance music and banjo hoedowns. Fellow Swede Max Martin has his production fingerprints all over Katy Perry’s new album. Norwegian duo Stargate are among the first Rihanna calls when she wants a hit.

Next week the Roundhouse in London celebrates the Nordic invasion with the Ja Ja Ja festival, a two-day event headlined by Danish acts Mew and the Raveonettes. It’s a far cry from the Hootenanny Singers with their sensible knitwear. But is there anything Nordic really going on here? Or is it just cultural mimicry, the copying of music from the UK and US, as though the region were a vast Brooklyn with fjords?

Abba in 1974

The trail begins with Abba. “No one would listen to Swedish music before Abba – we were door-openers definitely,” says Ulvaeus, who formed the band in 1972 with Benny Andersson, Anni-Frid Lyngstad and Agnetha Fältskog, all fellow veterans of Stockholm’s cabaret and pop scene.

From the beginning, the foursome targeted an international audience, a strategy often ascribed to their manager Stig Anderson but which Ulvaeus insists was their own choice. Early singles “Ring Ring” and “Waterloo” were initially recorded in Swedish so as to qualify for Sweden’s Eurovision Song Contest entry. “But,” Ulvaeus says, “the plan was always to sing in English afterwards.”

Co-writer with Andersson of almost all Abba’s songs, he reckons the band had a distinctively Swedish sound. “Swedish radio would play Italian ballads and French chansons and German schlager – a big huge mix. What comes out in Abba is a mix of all of that, which makes it exotic perhaps, and not what would have come out of a pen from England or America.”

Abba’s greatest hits compilation Gold is the UK’s second best-selling album of all time, behind Queen’s Greatest Hits and ahead of Sgt Pepper’s Lonely Hearts Club Band. But their 350m record sales were built on Swedish talent: most Abba songs were recorded in their homeland using local labour and resources, a vital source of experience for the country’s later pop boom.

The contrast with A-ha is telling. The Norwegian heartthrobs took over in the mid-1980s where Abba left off. But to do so they moved to London, where they worked with British producers and were signed to Warner Bros. Similarly, Iceland’s emergence on the pop scene with the Björk-fronted Sugarcubes came after the band signed to British and US labels in 1987.

Sweden stands apart from its Nordic neighbours in having the most sophisticated pop music infrastructure, a tradition that continues in the digital age: the song-streaming service Spotify was dreamt up in Stockholm. The country’s music revenues were up 12 per cent in the first half of 2013. Yet the domestic market remains small compared with more populous countries. Bands have an incentive to look abroad for audiences.

NoNoNo in New York, 2013

“Of course we were hoping for international success but were thinking, Sweden – it would be great if it would work out. We were never expecting for things to happen in the US and the UK,” says Stina Wäppling, singer with one of the country’s latest musical exports, NoNoNo. I catch up with her when she and her band mates arrive in New York to promote their electro-pop anthem “Pumpin Blood”.

Wäppling, who studied at a British university, sings in English. “So many of the movies we watch and so much of the music we listen to is in English that it can be more natural to sing in English than talk in it,” she says. But she concedes that singing in her own language is “closer to the heart, it’s more personal”.

There’s a notable lack of resentment among the acts I speak to about having to give up their own language. The difference from France, with its strategies for protecting the mother tongue from “les Anglo-Saxons”, is stark. It’s also a far more relaxed approach to authenticity than the British habit of policing its pop stars for “phoney” American accents.

“Icelandic is a harsh language,” says Ragnar Thórhallsson, co-singer and guitarist with Of Monsters and Men, the Icelandic indie band whose debut album was a top 10 hit in Britain and the US earlier this year. “We make a lot of sharp sounds and it’s not always easy to find rhymes. It’s a very straightforward, no-nonsense kind of language. English is very ‘flowy’: it’s easy to come up with rhymes.” His approach is pragmatic. “If our songs were in Icelandic, you’d probably not be interviewing me right now.”

Pop used to have regional identities. Performers were often seen to express the spirit of a place – Merseybeat in Liverpool, Philly soul in Philadelphia. Geographical rivalries were refracted in the charts – southern “softies” Blur versus northern “lads” Oasis. But technology has weakened locality as a defining characteristic; even in hip-hop, the most roots-obsessed of genres, it matters less and less where the music actually comes from. Tor Erik Hermansen of Stargate grew up in Trondheim, Norway, listening to early hip-hop and watching MTV. He now lives in New York and is one of the top producers in the US. “Hip-hop culture is international; it comes from all over the world,” he says. He doesn’t think his Norwegian background has much influence over his work.

So are there any Nordic pop traits? Ulvaeus mentions a common Scandinavian theme: melancholy.

“Someone described the music of Abba in a very interesting way when they said that the melodies are melancholic – very often minor key and very often the lyrics are very dark but somehow the arrangements and the two girls’ voices especially makes it sound kind of exuberant and uplifting still. It’s a paradox. That’s the best description I’ve heard.”

But there’s a marked absence of melancholy among current Nordic pop acts. Their success lies in the opposite direction – a robust adaptability, the uncomplicated ability to move between local and international. The jingoism of British and American pop is absent; and so too any hang-ups about authenticity. Among this handful of the richest and best-educated countries in the world, pop music has reached a state of pure exportability.

Ja Ja Ja Festival, Roundhouse, London, November 8-9. roundhouse.org.uk