Minor adjustments are huge in Sigur Ros’s world, so you could argue that Takk… (Geffen), the new album by the Icelandic quartet, is full of radical departures. Their songs now have titles, the lyrics are in Icelandic instead of the band’s invented language, Hopelandish, and the songs are more concise and glossy. Not that they’ve started using verse-chorus-verse structures and terse guitar solos on three-minute tunes, but their sonic trademarks–ethereal falsetto vocals, glacial pacing, and swirling, all-texture guitars–are reined in. Their songs still tend to be convoluted–the eight-minute-plus “Se Lest” drifts through three or four distinct permutations before closing with a relatively incongruous brass fanfare–but they come swaddled in strings, bells, and whistles. They’ve also tightened their dynamic range, making more patient and measured shifts and using fewer big rock crescendos. Takk… is more about refinement than retrenchment; I’d prefer to hear Sigur Ros push a little harder, but this is another lovely work. They’ll be backed by the string quartet Amina, who’ve long collaborated with the band; they’ve just released their debut record, a lovely instrumental EP titled Aminamina (The Worker’s Institute). Wed 9/21, 7:30 PM, Chicago Theatre, 175 N. State, 312-443-1130 or 312-902-1500, $29-$33. All ages.