Most of Francisco Lopez's CDs are packaged in clear slimline cases and come without recording information or titles. It's not because he's on a budget: the Spaniard insists that his pieces are pure sonic experience, free of any larger meaning: "I want to be flowing inside the sound instead of listening to it," he's said. Lopez draws from diverse sources--field recordings (often made in Latin American jungles), the work of fellow experimentalists, the occasional heavy-metal album--then manipulates the sounds beyond recognition. His music routinely pushes the extremes of audibility, ranging from extended silence to sustained waves of torturously loud noise. (The silences give the quietest passages a sense of scale and allow Lopez's wall of noise to be experienced brick by brick.) But instead of earplugs a blindfold was included in last year's CD Live in 's-Hertogenbosch (Bottrop-Boy), a tool to help focus sensory perception exclusively on the aural. Most of his performances occur in the dark for a similar reason, and it works: once you block out visual information, it becomes possible to get lost in the din, discovering layers of detail that would be missed on a more casual listen. Saturday, March 20, 9 PM, 6Odum, 2116 W. Chicago; 773-227-3617 or 312-666-0795.