In 2011, the band started the painstaking forensic task of piecing together a cohesive and magical work from disparate constituent parts. If this sounds unromantic, the results are anything but. Something alchemical occurs when the four members of Sigur Rós are in the room together, and even if Valtari is more a 'studio based' album than any of its predecessors (which usually start life as rehearsal room jams), the long hours of experimentation and unsentimental editing have yielded incredibly persuasive results.