Just a few years ago, the leading lights of the European free-music scene appeared in Chicago about as often as the Virgin Mary. There wasn’t much of an audience for their music because their import-only recordings were hard to come by, and not many promoters were willing to fly them over to play for a handful of people. But the explosion of the local free-music scene blew the lid off one of the country’s most sophisticated audiences, and when German trombonist Johannes Bauer made his long-overdue local debut in the fall at the Empty Bottle, the joint was packed. He returns this week with another European giant, Belgian pianist Fred van Hove, who last played here in 1997, and their duo performance promises angles we haven’t heard from them individually. Van Hove has done some of his most powerful playing since his last visit: on last year’s double CD Flux (Potlatch), he sculpted dense slabs of sound with thunderous, bass-heavy clusters, abrasive string scrapes, and furious single-note runs with astonishing agility. Bauer, who plays with the pianist regularly, has plenty of power himself, but whereas van Hove’s music is seriously, almost monolithically dark, the trombonist has a keen sense of humor and likes to crack a musical joke here and there. Part of the thrill of this concert will be finding out how far each man will venture out to meet the other. Wednesday, 9:30 PM, Empty Bottle, 1035 N. Western; 773-276-3600. PETER MARGASAK

Art accompanying story in printed newspaper (not available in this archive): Fred Van Hove uncredited photo/ Johannes Bauer photo by Dagmar Gebers.