Daniel Barenboim is using his baton as a stiletto. The outgoing musical director of the Chicago Symphony has lashed out against Muzak in a BBC lecture series. Starting in the 1920s, Muzak pioneered the piped-in music that follows you around like a talkative acquaintance with bad breath. Barenboim called it "absolutely offensive" and declared, "active listening is essential." In response, the Muzak people compared their product to the works of Erik Satie, describing it as an "aural background" and a "mood enhancer." But the conflict here isn't between foreground and background listening. It's between music voluntarily perceived as music and music involuntarily endured as noise.