The experimental electronic pop of Iceland’s Múm got a boost with its fourth album, Go Go Smear the Poison Ivy. A lineup change added two new vocalists, giving the group's music a significantly different feel. That move toward a more organic, acoustic sound continues on Sing Along to Songs You Don’t Know; Múm's sound sweetly blooms, and many of the tracks here take on the feel of sophisticated children’s songs. The skittering Jew’s harp and ukulele on “Prophecies and Reversed Memories,” the meeting of strings and cowbell on “The Smell of Today,” and the marimba twinkle of the charming “Blow Your Nose” are full of glee and whimsy. The delightful "Húllabbalabbalúú" swings and sways (it’s much easier to say than the eye thinks it would be) with trumpet and marching tom drums, while a slide guitar hints at Hawaiian music alongside twinkling dulcimer on “If I Were a Fish.” A gentle chorus of voices wafts above a beautiful, solitary acoustic guitar on the all-too-brief “Last Shapes of Never,” an autumnal ballad that one would never have expected from Múm a few years ago.