Persistence and accessibility set the German duo Cluster apart from their fellow krautrockers. Can was more diverse, Faust more avant-garde, Kraftwerk more explicitly ideological--but they've all broken up or taken 20-year breaks between albums. Cluster's Hans-Joachim Roedelius and Dieter Moebius, on the other hand, have been making electronic music that sounds warm and organic for 25 years now, and although not as well-known as their contemporaries, they're every bit as significant. Cluster's two late-70s collaborations with Brian Eno (now available domestically for the first time as part of Gyroscope Records' effort to reissue the band's back catalog) profoundly influenced Eno's subsequent immersion in atmospheric instrumental music. And the twosome's blend of placid soundscapes, wistful melodies, and pulsing rhythms on the records Sowiesoso and Grosses Wasser presaged the current generation of ambient techno artists. Moebius and Roedelius also joined Neu's Michael Roether in the group Harmonia, whose metronomic beats are the foundation of Stereolab's rhythmic approach. On the pair's most recent album, 1995's One Hour, improvisations juxtapose glassy textures and chirpy blips so elegantly that they sound carefully composed. This concert is part of Cluster's first U.S. tour. Rome, the Brain, and local ambient DJs Atmospheric Audiochair will also appear. Friday, 10 PM, Metro, 3730 N. Clark; 549-0203.