“I believe that music should be collective hysteria and spells, violently of the present time,” composer Pierre Boulez wrote in 1948, and Alex Ross would agree—love of spirited innovation infuses his tremendously absorbing history of modern composition, The Rest Is Noise: Listening to the Twentieth Century. The book not only goes a long way toward explaining why folks such as John Cage and Harry Partch made all that racket—it smartly positions the music within larger political upheavals. The world wars atomized both composers and composition­: Schoenberg and Ligeti went into exile, Strauss and Shostakovich (at least publicly) sympathized with tyrants, and Romantic tradition was snubbed in favor of 12-tone music, Karlheinz Stockhausen’s splattery electronics, and masterfully layered drones like Steve Reich’s Music for 18 Musicians. Ross, the New Yorker’s classical music critic, travels from The Rite of Spring to Nixon in China without picking ideological sides­; he openly embraces the mix of jazz, classical, rock, and electronic musics the century produced. He’s not without his hobby horses, though: In steering the narrative toward themes of emotional, compositional, and political fracture, his polestar is Benjamin Britten’s 1945 opera, Peter Grimes, whose hero is the archetypal displaced person. People come first for Ross: He knows his theory, but he’ll lay off the jargon to find the right metaphor or anecdote to expose how the music wounds and heals. To him, Schoenberg’s notes drip “like blood on marble,” and he knows there’s no better way to explain the postapocalyptic quietude of Arvo Pärt’s Tabula Rasa than to note how AIDS patients have hungered for it on their deathbeds. Ross discusses and signs copies of his work at 7 p.m. at Politics and Prose, 5015 Connecticut Ave. NW. Free. (202) 364-1919.