Ólafur Arnalds, Queen Elizabeth Hall

Ólafur Arnalds used to drum for a hardcore band called Fighting Shit. But since 2007 he’s produced a string of achingly emotive CDs that integrate sparse piano, keening strings and subtle electronic texture. He’s Icelandic and, inevitably, his instrumental music is usually described as evoking empty landscapes and long stretches of darkness. But judging by last night's concert, his sunny outlook, affability and humour cut dead all thoughts of dark nights of the soul feeding his muse.

A stately piano piece, based around a series of repeated and building arpeggios titled "Poland" wasn’t a reflection on the country. It was, he said, written following an overnight bus ride during which he couldn’t sleep as the roads were so full of pot holes. He decided that drinking might make him fall asleep. It didn’t. Feeling sick, he arrived at the next day’s show and wrote "Poland" in five minutes during the soundcheck. Another yearning instrumental was written to soundtrack an ad for bathtubs. The advertising agency, he said, rejected it as not silly enough. He delights in puncturing expectations about his inspirations.

Even so, the contrast between Arnalds's affable, bantery personality and his introspective, Minimalist music is marked. But, like the jump from hardcore punk to classically tinged melancholia, Arnalds isn’t simple to interpret. The inspiration for his move into this music was the soundtracks to The Green Mile and The Shawshank Redemption. He’s no tortured composer – he’s massively prolific. Eulogy for Evolution was issued in 2007, Variation of Static in 2008, Found Songs and Dyad 1909 were released in 2009. …and they have escaped the weight of darkness arrived in 2010. Found Songs was the result of writing and recording a song a day over a week, and putting each up for download at the end of the day. He tours relentlessly. His energy levels are more in keeping with his punk background than the modern classical world his music points towards.

Last night, he played a grand piano and was accompanied by a string quartet and a chap dealing with the electronics. Strip away the latter and he could be a successor to Delius and even Lark Ascending Vaughan Williams. The string parts he writes are structured around refrain, rather than straight melodies. Each phrase jumps to, or, more often, glides down to the minor. Violins interweave, rather than layer. His music is grounded in the pastoral. Nico Muhly is a kindred spirit. (Ólöf Arnalds is his cousin.)

Of course, string-centred musical melancholia from Iceland is always going to draw comparison with fellow Icelanders Sigur Rós. The set opened with “Þú ert Sólin” from …and they have escaped the weight of darkness. The only similarities with Sigur Rós were the mood and presence of strings. Arnalds’s compositions aren't about building textures, layering sound on sound, but about subtly altering refrains as passages pass. “Tunglið” and “Loftið Verður Skyndilega Kalt” followed, as they did on …and they have escaped the weight of darkness. As the set progressed, Arnalds ranged through his whole catalogue, introducing some as yet unrecorded material (including “Poland”).

There is great beauty in Arnalds's music. Great sadness too. His chirpiness is initially confounding. Yet as he sat playing, he swayed, lost in his music. There is no filter; Arnalds is his music.

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Watch the video for “Hægt, Kemur Ljósið” from Ólafur Arnalds’s …and they have escaped the weight of darkness