Non-neutral material is critical. It is the only way of relating local, regional, and global levels, and escaping the model of an empty global form filled with replaceable local objects. Why is the latter approach incorrect? For ideological reasons on the one hand and for musical reasons. Ideologically it has to do with the affirmation of music as a separate sphere of thinking, and thus with an affirmation of materialism. Musically it is simply a fact that non-neutral material is more interesting and more full of possibilities.
Non-neutral material means that all local objects must have an interiority of a certain degree of complexity (neutrality is the opposite: the object is internally homogenous and stable). This interiority must be a certain balance of regularity and irregularity. This interior structure is then capable of giving its own continuation, or, at least of providing links with other material. In other words, that local material has a bearing on global form, and vice versa.
It is not clear what the relationship between the interiority of the object and the contradiction is. Must the interiority be produced by a contradiction? Or is the contradiction only one specific operator? A privileged operator?
It is true that all non-neutral material today will be at first contingent in character and not properly a line of novel thought in music. The point is to start to construct a project through testing possibilities, but the point is that this testing must take place within the space of non-neutrality.