Simplicity is the key to success at the moment for First Aid Kit. On the face of it, there’s nothing especially remarkable on show here. Sisters Klara and Johanna Söderberg play a very straightforward folk music – simple melodies; glorious harmonies, it’s comfortingly familiar stuff. And yet, there’s something of an air of greatness about them.

Partly, that’s due to their charm on stage but mostly it’s down to Johanna Söderberg’s glorious, soaring voice. Her handling of Fleet Foxes’ Tiger Mountain Peasant Song is immaculate and seemingly effortless.

Much more than that though is the feeling that this is only the very beginning. The sisters are impossibly young (they are still chaperoned by their father who acts as soundman during their tours) and can only get better. Already, they are able to do the simple things stunningly well, once they begin to develop further and start to push the boundaries of their music, who knows what they will be capable of.

That autoharp which Klara is clutching might only be the start.

The Westgarth Social Club in Middlesbrough may be an unlikely setting but it’s building an impressive reputation for being one step ahead of the game. So far in 2009 promotors, The Kids Are Solid Gold, have brought, amongst others,  Canadians Woodpigeon, American whispering folksters Horse Feathers and probably most impressively, The Leisure Society who packed the venue out just weeks before landing an Ivor Novello nomination. Tonight the joint headline tour of First Aid Kit and Fanfarlo are at the venue. It is what is says it is on the label – a social club function room – but once the lights go down its as intimate a venue as you would want and a place where bands seem to love to play, with many citing their shows at the Westgarth as tour highlights. It is, in its own way, similar to the Band Room in North Yorkshire, only without the breathtaking scenery outside and having the advantage of having an inside toilet and a good pint of beer on tap.

First Aid Kit specialise in folky harmonising with a distinct Swedish accent, which isn’t surprising as they are from Sweden. They are also sisters and impossibly young to be producing music as well written and performed as this. A mixture of wistfulness and dry wit, their songs are melancholic without being overbearing. Most of their excellent Drunken Trees mini album gets an airing including their cover of Fleet Foxes Tiger Mountain Peasant Song. It’s a huge gamble and it pays off because their voices are strong enough to carry off both the harmonies and the soaring solo impeccably. They are a band that will only get better.

Fanfarlo however are already very much the finished product. Looking like the cast of a Cohen Brothers film, they are a strangely entrancing bunch. Comparisons to Arcade Fire may surprise some but their songs share a similar structure. Where Arcade Fire crank up the noise though, Fanfarlo create a wall of sound by layering strings, horns and keyboards over the guitar and mandolin. Also like Arcade Fire, their lyrics have a literary feel to them and every song becomes a novella read in a voice with more than an echo of David Byrne.

Three encores tell their own story and by the end you feel they have probably just about run out of songs, with their debut album Reservoir having formed the backbone of the set. The only mystery is how the almost overwhelmingly great Fire Escape, the highlight of the album, is almost overlooked. Called for by the audience the band concede that ‘Oh yeah, we could play that.’ What follows is about the most you can hope for from live music. The song is worthy of obsession, which is handy as that’s where I’m headed with it.

Already hailed by David Bowie, gaining increasing radio play and having just completed a sell out tour of America, there probably won’t be too many more opportunities to see Fanfarlo in a venue like this. That’s a shame, but as Fanfarlo move onwards and upwards, the Westgarth will be most probably be providing a home for next year’s next big thing.

To find out what’s up next at the Westgarth click here.

Fanfarlo live here.

First Aid Kit can be found here.