An intertwined crash course in outsider music and cultural studies, Paul Hegarty’s dense new survey, Noise/Music: A History, traces noise music’s avant-garde and experimental roots—from Futurism, Fluxus, and musique concrète to 1970s progressive rock and punk—and examines its more recent incarnations. In his attempt to characterize “noise,” Hegarty (who, in addition to teaching philosophy and visual culture, plays in two noise outfits) admits that the concept doesn’t have a static definition; it can be designated only by context. Still, he asserts that the music “largely avoids song structure,”