First Aid Kit @ Shepherd’s Bush Empire, London

First Aid Kit have proved one of the biggest, albeit low-key successes of 2012. Their second album, The Lion’s Roar, released in January, has gained momentum throughout the year – so much momentum in fact, that they’re rounding off the year with their biggest show to date – a sell out night at Shepherd’s Bush Empire.And when we say sell-out, we mean sell-out – every tier of the former theatre is teaming with people. “Wow, this place is big” gasps Klara Soderberg, when the spotlights rise for the first time. When she and her sister Johanna finally get chance to stop and reflect on the last 12 months, they’ll probably have a similar reaction.

This year was four years in the making; back in 2007 the Swedes first made a name for themselves by posting their take on Fleet Foxes‘ Mountain Peasant Song on YouTube. Their debut album – a record filled with dreamy folk – followed a couple of years later but it was The Lion’s Roar, released back in January, that catapulted them. Its beauty lay in its subtlety; simple but awash with imagery that transported listeners straight to their hometown of Stockholm – it was in equal parts sentimental, heartbreaking, romantic, dark and spooky.Those themes are effortlessly transferred onto the stage tonight, and the band enter to a stirring instrumental as sketched images of trees are projected onto the back of the stage – the only light across an eerily still room. The Soderbergs add to the spookiness by wearing their long hair over their faces, and waving their flowing sleeves around as they open with In The Morning, from The Big Black and Blue.

The first half of the set follows this formula; haunting balladry against a backdrop of dimmed light displays – most of the songs are taken from their debut and Klara in particular excells herself.The sisters stand on opposite sides of the stage, staring out to their audience, but fail to really draw them in until they announce: “We’d like to abandon modern technology for a second” before downing their guitars, stepping away from their mics and joining each other at the front of the stage. There begins an a capella, unplugged version of Ghost Town – a brave move in a venue this size. It silences the chatter that had begun to spread across the room, and their request for everyone to sing along provokes a gentle, whispered response – singing in their key proves tricky for most – but it’s a gear shifter and this warm, campfire moment sparks a more energetic second half.

Most of this section’s songs are lifted from The Lion’s Roar, with its more rounded sound and thudding drums, as the venue’s mirrorball casts snow-like lights onto the stage and the Soderbergs headbang their way through a fiestier selection of songs. The likes of Wolf Mother comes to life, and they thrash their long hair around with endearing, if unexpected,enthusiasm.They take a break from rocking out for album highlight Emmylou – “A song about incredible voices”. With its references to Ms Harris, Gram Parsons, June Carter and Johnny Cash, it gives an insight into their musical upbringing, as does their choice of encore – Simon and Garfunkel‘s America.

As the crowd files out onto a rainy Shepherd’s Bush Green, it’s almost a shock to be confronted by a dark, drizzly roundabout, rather than the vrisp, bright snowy picture First Aid Kit painted. But the songs linger for longer – tonight felt like something of a victory parade; a perfectly constructed set that charted their rise from purveyors of delicious folk harmonies to something altogether more forceful.