For well over a century musicologists have been fascinated by composers' manuscripts and by the insights they might reveal about the nature of musical composition. This book suggests ways in which Debussy's sketches and drafts may be used to explain how he composed one of his last great symphonic scores: Ibéria (from Images for orchestra, 1903-10). Part 1 shows how we might understand the process of musical composition as a form of expert problem solving; it describes the compositional history of the work, the various intentional goals and historical constraints that guided Debussy's thinking, and some of the technical problems Debussy faced while composing this remarkable score. Part 2 reconstructs the genesis of each of the three movements in turn.