The first single for Sigur Rós’ Valtari, “Ekki Múkk,” arrived with the fanfare and warm reception expected of that dramatic moment — after all, it was the first new recording under the Sigur Rós banner since 2008′s Með Suð Í Eyrum Við Spilum Endalaust. “Ekki Múkk,” though, isn’t much like the Icelandic group’s best known [...]