First came Bjork, then Sigur Ros; the latest product of Iceland's prodigiously hyped music scene to make waves in the international press is the quartet Mum (rhymes with "broom"). They first caused a stir last year with their debut, Yesterday Was Dramatic--Today Is OK (Thule), which eschewed both the epic, ethereal grandeur of Sigur Ros and the extroverted eccentricity of Bjork in favor of something modest, meandering, and childlike. The music combined a gentle backdrop of gurgling, subtly glitchy electronics with streaks of live instrumental color--accordion, clarinet, glockenspiel, guitar--but the band's pretty songs and soft-focus ambience didn't stray too far from the aesthetic of shapelessness made fashionable by the laptop-loving minions of the IDM scene. The album's delicate, sentimental melodies billowed like cumulus clouds in a time-lapse movie, folding back in on themselves and constantly changing form. On Mum's new album, Finally We Are No One (Fat Cat), they retain the electronics as a foundation, but overall the music sounds more organized, with more elements clearly in the foreground. Twin sisters Gyda and Kristin Anna Valtysdottir sang sparingly on the debut--it was just another texture--but here the songs often coalesce around their fragile, innocent-sounding tandem vocals. Mum still doesn't embrace verse-chorus-verse structures, but they've strengthened their whimsical melodies with a more pronounced use of live instruments--trumpet, melodica, cello, bass--which function as a kind of sonic skeleton. Though the music is undeniably beautiful in its hermetic purity, it's clearly the product of multiple overdubs rather than a band playing together in a room; it's hard to imagine it coming off with the same precision onstage. This is Mum's Chicago debut. Thursday, July 18, 9:30 PM, Empty Bottle, 1035 N. Western; 773-276-3600.