bandpass

I believe that we respond to and recognize something about the shape of the change in a sound, and that shape forms a metaphorical sonic "gesture" in our minds. The "shape of the change" means the way in which some aspect of the sound (it could be any measurable parameter) or the music (it could be any characteristic we care about) changes over time: how radically it changes, and with what acceleration of change. That can be simply stated as the value of the parameter in question, depicted as a function of time. That is, the "gesture" can be depicted as a curve of change over time.