The latter part of the 1950s saw a major change in Boulez's compositional approach: Instead of creating extensive pre-compositional sketches, he increasingly reused previously composed materials as the basis for new works. The shifting aesthetics that characterized this period had a
significant influence on Boulez. His works from the late 1950s explore the ideas of mobility embedded in the open work. Balancing the concept of mobility with the ideals of control that form the basis of his compositional ideology led to an economy of means and an associated emphasis on the
concept of development in his compositional process. Both facilitated the creation of new works from a more limited array of base materials.<br/> Tracing the concept of development in a sample of Boulez's sketches and works from the late 1950s through the 1960s, this essay presents a
preliminary typology of recurring pitch and temporal developmental techniques. By taking a bird's-eye view, I add an additional level of interpretation, emphasizing their formal function, association with aspects of middleground structure and studying their implications in terms of perception.
In this way, I present a new perspective on the association between these techniques and the practice of derivation from a limited amount of material that characterizes these works.
A Compositional Approach to Probabilistic Knowledge Compilation