While they haven’t quite turned into Rubberbandits, there have been distinct signs of a thaw from Sigur Rós over recent years. For their last LP they even consented to interviews (earlier media appearances had been sulky and monosyllabic, tooth-pulling exercises for all involved). Then, 18 months ago, singer Jonsi Birgisson released a solo project that was almost a pop album (or at least, a pop album as recorded by someone with a working knowledge of Olde Elvish). Hopes that he might bring this freshly-cultivated exuberance back to the day job are, alas, dashed by Sigur Rós’ sixth record, a meditative affair full of moments of grace but without any of the drama that has attended their best music. Guitars are almost entirely absent, the foreground occupied by Jonsi’s wispy voice, tinkling piano and mossy backwashes. There’s a liveliness to ‘Varuo’ that suggests it might lead somewhere but the song ultimately folds inwards; on ‘Rembihnutur’ ethereal bleepery feels like an end in itself, the tune lost in reams of aural shagginess. Valtari is sweet and blissful but, in the end, fatally somnolent.