SIGUR RóS Kveikur [XL] What is it about Sigur Rós? By rights, this Icelandic band shouldn’t be anywhere near popular enough to headline Madison Square Garden or appear on The Simpsons, and yet in the first half of 2013, they’ve done both, building anticipation for this, their seventh album of elliptical, ethereal, strangely enchanting “dream rock,” as many describe their sound. This time out, “nightmare rock” sometimes seems the better...