On ( ) (MCA)--yes, ( )--its hotly anticipated follow-up to 2000's Agaetis Byrjun (Fat Cat), the Icelandic quartet Sigur Ros mostly leaves well enough alone. But the new album--eight untitled songs, clocking in around 70 minutes and recorded at the band's new Reykjavik studio, a converted swimming pool called Alafoss--does scuff the ethereal polish of its predecessor ever so slightly. The drums sound crisper, the androgynous vocals of Jon Birgisson more sibilant, and the guitars more like guitars--except, of course, when they're being played with violin bows. But the arrangements are still dense--the group's trademark guitar arpeggios, swirling keyboards, squirmy electronics, and hydroplaning cymbals are now more prominently augmented with lush strings. As on the last album, most of the songs progress majestically from hush to thunder, interrupted only occasionally by flashes of acidic guitar noise. Birgisson still sings in his invented language, Hopelandish, and with no overt meaning to weigh them down, his lyrics become just one more layer in the band's signature dreamy drone. With their dynamic performance style and the addition of Amina (the string section on the album), Sigur Ros are likely to succeed in bringing the material to life onstage. Still, I hope they try something new soon. Sunday, November 10, 7:30 PM, Riviera Theatre, 4746 N. Racine; 773-275-6800 or 312-559-1212.