Music: Crack in the Wall

For much of the 20th century, many leading avant-garde composers have arranged their notes, rhythms and timbres according to predetermined schemes or series. Such major works as Arnold Schoenberg's Serenade and, more recently, Pierre Boulez's Le Marteau sans Maître have been serial compositions. Indeed no one has championed serialism more than has Boulez, the onetime enfant terrible of French music who is now the 47-year-old conductor of the New York Philharmonic and the BBC Symphony. Yet there was Boulez in Manhattan last week introducing his new 31-minute composition . . . explosante/fixe ....