Dawson Prater, the proprietor of Locust Music, devised the clever concept behind "Object," his label's series of free-improv records: the musicians are shown a picture of some inanimate objects and asked to "interpret" them. So far the releases have been superb, and the question of how the music relates to the items pictured on the disc's cover encourages active listening. The cover of the CD from the Chicago duo EKG (single-reed master Kyle Bruckmann and trumpeter Ernst Karel, both of whom also contribute electronics) shows a frayed electric cord, a matchbook, and some magnets, and it's not too hard to connect those items with the low hums, high tones, noise blasts, and sizzles on the disc. The duo blurs the lines between acoustic and electronic, and sound sources are often impossible to pin down, though the puckered air shooting through Karel's trumpet and Bruckmann's tongue popping on English horn do stick out of the din. Their warm tones rise and fall like a raft hugging the waves only to be met with unexpected bumps--a startling noise here, a cluster of electronic clicking there. The CD by cellist Fred Lonberg-Holm and German trumpeter Axel Dorner features images of a bowling ball, a lung X ray, and a Brillo pad--this one's a little tougher to decipher. Dorner's remarkable technique enables him to make noises you wouldn't expect from a trumpet: sour squeals, quickly looping columns of air that sound like an engine trying to turn over, and blubbery flatulence. Lonberg-Holm matches him step for step, punctuating his creaky bowing with scratches, scrapes, and stuttered thwacks. Dorner can't make the gig, so Lonberg-Holm will improvise with a videotaped performance by the trumpeter that he's never heard before. Friday, April 18, 9 PM, 3030, 3030 W. Cortland; 773-862-3616.