The Breton capital Rennes is an attractive city. Move north from the train station, pass through a covered market with tripe and saucisse sellers, cross a canal and there's a series of Italianate squares and arcades. Further along is the quaint Place St Anne and a warren of medieval streets lined with half-timbered buildings. It’s an inspiring cityscape. But for three days every December, the city is crammed with revellers and dogs on string who couldn't give a fig about the medieval cathedral. They're here for the Trans Musicales de Rennes, the annual musical jamboree.

There’s something going on in the North. Iceland’s Hjaltalín incorporate a disco sensibility and Sweden’s Concretes draw from the same well on their new album WYWH. Although this is probably not the future direction of Nordic music, it’s now an important part of it, showcases a reinvented Concretes and, judging by last night’s show, they might as well be a new band. Although still glacial – you could never imagine them breaking a sweat on stage – this show drew a curtain on their past.

There’s a moment during Hjaltalín’s encore when bolero rhythms take over and you wonder if the Reykjavik septet have invented a new musical hybrid: a Ravel-driven makeover of Seventies-slanted soul. As singer Sigrídur Thorlacius lets rip on the thrillingly anthemic “Feels Like Sugar”, it’s clear that Hjaltalín aren’t bothered with current musical templates. They take from the unlikeliest sources, smoosh them together and end up sounding like no one else. After all, this is a band with a stand-up bassoon player.

Although Danish singer-songwriter Agnes Obel has professed a kinship with Roy Orbison and his grand musical dramas, it’s John Cale that she covers on her debut album. Choosing the slow-burning “I Keep A Close Watch” from 1975’s Helen Of Troy (Cale re-recorded it in 1982 on Music For A New Society) is telling. Not only does Obel look for and seek to telegraph emotion, she is allying herself with performers and songwriters recognised as passionate and heartfelt. After her openness, it’s fair to ask whether Obel is similarly affecting.

The music of Sibelius might speak of Finland, its unpopulated spaces, vast inland lakes, semi-Arctic climate and long, dark nights, but the annual Lost in Music festival brings together a bewildering array of Finnish bands and singers that range from rockabilly and ska to introspective folk and – of course, the national staple – heavy metal.

Twenty-five years ago, a-ha achieved something unprecedented for a Norwegian band: they entered the British charts. The week of 5 October, 1985 saw “Take On Me” enter the Top 40. Three weeks later it peaked at number two. To mark the anniversary, a-ha have chosen to do two things: embark on a worldwide farewell tour and play a special show at the Royal Albert Hall, running through their debut album, Hunting High and Low, with a full orchestra. That not being enough for a full show, they also played its follow-up, Scoundrel Days.

Last year’s Vid og Vid (an Icelandic colloquialism for "every now and then"), Ólöf Arnalds’ debut album, attracted some high-profile fans. Fellow Icelander Björk raised the flag on America’s National Public Radio, as did Jonathan Richman who requested that she open the shows during his San Francisco residency last week. Björk has contributed vocals to "Surrender", a cut from Arnalds’ forthcoming album Innundor Skinni (Within the Skin).