Sigur Rós' dreamlike post-rock is often beautiful and cinematic—but the Icelanders are also capable of painting starkly different pictures. Since 1999's Ágætis byrjun, the band has dipped into the depths of a post-apocalyptic world in ( ) and incorporated downhome folk in Takk…. These cuts mark the directions the group have taken—and hint at where they might go next.