Caught Live: First Aid Kit + Samantha Crain @ The Workman's Club, Dublin

First Aid Kit have come a long way since their last visit to Dublin. That was almost three years ago, when the Swedish sibling duo opened for compatriots Peter Bjorn and John just around the corner at The Button Factory. As the pair fondly reminisce this evening they were "still in school" back then, and while age may not exactly be creeping up on them today (the younger Klara is not yet out of her teens), much water has passed under the bridge since that night.

Last year alone saw them being headhunted by Jack White, as well as reducing Patti Smith (of all people) to tears at Sweden's Polar Music Prize ceremony. The sisters also relocated to Mike Mogis' famed Omaha studio to record January's incandescent The Lion's Roar LP – a stark contrast to 2010's homebirthed debut, The Big Black and The Blue – where they worked alongside a revolving cast of Saddle Creek alumni, including Bright Eyes' Conor Oberst and Nate Walcott. That sophomore effort has since conquered the Swedish album charts, and even managed to trouble the UK Top 40 upon its release.

Tonight's Workman's Club show has sold out weeks in advance, affording the Söderbergs yet another reason to smile. Not that they really seem to need one: effortlessly cute and cheerful onstage, their soaring Patsy Cline-duetting-with-Neko Case harmonies are immediately to the fore on opening number 'This Old Routine', Klara allowing herself a quick giggle as she briefly miscues on guitar. This homely feel is soon washed away, however, by 'Hard Believer' from that aforementioned debut. A fiery rebuke against the "delusion imagery" of religion, they tell us the song is dedicated to Richard Dawkins. 'In The Hearts of Men' displays similar conviction, albeit of a more subdued nature. It's a gorgeously sad minor-key lament about fractured identity and the sands of time ("The parts we play to convince others..."), Mattias Bergqvist's lonely civil war drumroll beautifully underscoring Klara's forlorn lead vocal.

The girls' natural, down-to-earth rapport with the audience is displayed on a stunning unplugged rendition of 'Ghost Town': Johanna initially has her work cut out attempting to shush a few persistent talkers – this is a Saturday night, after all – before the pair are nearly drowned out by a crowd choir during the final chorus. At its core First Aid Kit is a band that relies on the power of the human voice, and this spine-tingling singalong offers a wonderful demonstration of just that.

Of course, they're also a group who in many ways made their name with a viral YouTube cover version. It's no surprise, then, that they should turn their hands this evening to another reworking, as they transform Fever Ray's ghostly 'When I Grow Up' into a jaunty-but-defiant ode to the idiosyncrasies of womanhood (those Swedes seem to have a thing about covering each other's songs, don't they?!?). Lovely as this is, it serves as mere window dressing next to some of their own choicer compositions: highlights include 'New Year's Eve', which boasts some nifty autoharp from the elder Söderberg, and the stirring 'Wolf' – arguably their most 'Fleet Foxesesque' number – which has heads nodding in approval.

"Folk n roll!" is the mantra these gals abide by, and the second half of that description could certainly be applied to the latter stages of tonight's gig. The Lion's Roar's anthemic title cut tonight transcends its cumbersome lyrics and foreboding tone to become a rollicking barn dance waltz The Carter Family would be proud of. Set/album-closer 'King of The World', meanwhile, is a full-on clapalong delight, the sisters seemingly striving to outdo one another in the hair-flailing rock out stakes.

To a certain extent, superb current single 'Emmylou' (wisely aired early on this evening) acts as a roll call of FAK's countrified influences. And yet, the song's simple, unaffected charm – not to mention the earthy beauty of those live harmonies – also neatly encapsulates everything that's great about this band. "With each secret revealed, there's another to be told" intones Johanna at one point on the sombre 'Dance to Another Tune'. On tonight's evidence, there's no reason for these guys to remain a secret for much longer.

(Special mention must go to diminutive support act Samantha Crain, who reemerged during the encore with the news that she'd just gotten engaged moments previously. Cue scenes of surprised celebration followed by a beautiful ensemble rendition of Crain's own 'The Dam Song', taken from the Oklahoma songwriter's 2009 LP, Songs In The Night.) 

Samantha Crain: 

First Aid Kit: 

Photos by Colm Kelly