Contrary to the prevailing wisdom, not everybody making flossy, disco-derived pop in the 80s was a clueless dip. Vince Clarke is a songwriter of the first water who helped found three of the most important bands in synth pop--and unlike, say, Henry Rollins, he kept making interesting music as a grown-up. Extravagant and sentimental, Erasure splits the difference between Clarke's other two big-name projects, combining the overheated melodrama of Depeche Mode with the boinky bubbliness of Yazoo. In 1985 Clarke picked 21-year-old unknown Andy Bell to be the gloriously gay voice of the duo, and since then they've released 11 albums, none of which wants for a bittersweet treat or three. These days Erasure sounds a little more dated than their synth-pop progeny, but the new Nightbird (Mute) hangs together better than some of the band's much-loved early records--The Innocents launched hits like "A Little Respect" and "Ship of Fools," but it had its share of duds. Erasure continues to inspire the classic synth-pop scene, which by now is a far-flung clan of never-say-die fans, united by the efforts of labels like A Different Drum, whose roster includes Cosmicity and Spray. It sounds like Clarke and Bell still pay attention to that scene too--Nightbird, darker and smoover than most of their work, brings to mind current continental groups like Wolfsheim. Last year Bell had both hips replaced and in December he announced he's been HIV positive since at least 1998, but reports from the road say he hasn't lost a step. Erasure also plays Saturday, and both shows are sold out; Elkland opens. Fri 4/29, 7:30 PM, Chicago Theatre, 175 N. State, 312-443-1130 or 312-902-1500, sold out. All ages.