Abstract
The main part of Boulez's last lecture at the Collège de France - "L'œuvre: tout ou fragment" (The work: whole or fragment) - deals with the different types of relationship that the fragment and the whole can have within the work , depending on the degree of integration of the former into the latter (from the simple collection - the album composed of detachable sheets - to the skilfully organized work, asserting itself as a self-contained totality). It's only at the end of the lecture that the perspective is reversed, with the apparently finished work revealing its fragmentary nature: the paradox of an unfinished whole, for which Boulez coined the concept of spiral form. In so doing, Boulez spends little time on the role played in his music - and the forms it takes - by provisional incompleteness: many of his works, even when they present themselves as finished, are only the states of a project whose realization has remained partial - the unfinished, and even the provisional, having, for contingent reasons, become definitive, or remained definitively provisional. To illustrate this point, we shall consider two very different cases, one from the first, the other from the last period of the composer's output: the Quatuor à cordes, which became Livre pour quatuor, and Incises (developed in sur Incises).
