This paper discusses the problem of motion processing and proposes the use of a mathematical model, which describes a motion signal as a path with variable harmonic components. We show that this model is quite suited to representing a motion path as a periodic part with additional motion texture (noise), as described in [18]. This provides a good mathematical formulation to the idea of “motion content”. We also describe some mathematical tools that can be used with the model in order to construct different motion path filters. As an application, we describe an algorithm to change automatically the time duration of a motion. We also point to interesting research directions on motion processing, using the model here introduced.