These Icelanders have always had a sideways relationship with the ideas of “pop” and “heavy.” Ambient mindblowers like 2002’s brilliantly titled ( ) drift and surge rather than swing, but the effect can be sublime and overwhelming. Kveikur has structure and, hello, grit like never before. (The drum-thunder shimmering vocal hook on “Ísjaki”! The distorto bass on “Brennisteinn”! All that riff fuzz on the title track!) Singer-guitarist Jónsi is still bafflingly obtuse – maybe he’s falsettoing in Icelandic, maybe it’s nonsense – but with no keyboards in sight, Sigur Rós are that most rock of entities: the power trio. Come on feel the noize.