Sigur Ros
Roundhouse, London NW1

Acceeding to the imperative to go beyond the power of their acclaimed and idolised studio releases by playing live, Sigur Ros offer up a moving and unforgettable performance at this iTunes festival performance.

The attention to detail in the arrangements of strings, wind instruments, keyboards, glockenspiel and sounds derived from the natural world heighten the emotional intensity of an experience which veers from the light to dark and bewitching.

Fronted by convulsive front man Jonsi Birgisson with his frenzied bow and guitar-work and falsetto delivery — a wordless kind of poetry — his is a gripping display of vocal bravura.

Recent releases Hrafntinna, Isjaki and Kveikur, which open proceedings, instantly set the sustained and heavy level agenda before the onslaught and tension of Svefn-q-englar. That’s followed by the calm of Hoppipolla, the raising of sonic temperature in Glosoli and the piercing sounds of Saeglopur.

Georg Holm’s bass riffs ripple, then strike hard and Orri Pall Dyrason’s percussion, wonderfully relentless, is a measured act of high tension which moves effortlessly between the primal and sublime.

Popplagi, the final cataclysmic moment of the set, typifies the band’s wild and beautiful performance throughout.

A unique act of expression, produced from an incredibly dense community of quasi-orchestral sound, Sigur Ros’s intent goes down a storm with the crowd.

Sigur Ros tour Britain in November, details www.sigur-ros.co.uk.