More re: Boulez:

"The way we conceive of the world of sound has long tended towards standardization of all its phenomena, at whatever level of pertinence they operate. The exclusion of all scales other than major and minor modes, and the establishment of equal temperament, was motivated by the most stringent standardization, allowing only a limited number of relationships within a given set of functions. Our instrumental world has tended towards purity of sound, according to one or another timbre, reducible to an abstract idea that can't be easily embodied in a previously established pitch hierarchy."