Becoming-Music. We have tried to define in the case of Western music (although the other musical traditions confront an analogous problem, under different conditions, to which they find different solutions) a block of becoming at the level ofexpression, or a block ofexpression: this block of becoming rests on transversals that continually escape from the coordinates or punctual systems functioning asmusical codes at a given moment. It is obvious that there is a block of content corresponding to this block of expression.