Tonematrix by André Michelle is a function defined on the two-dimensional vector space over the field . And yet, it’s so much more; though self-explanatory, it might save you three seconds to know that the axes correspond to time and pitch, with the latter staggered non-linearly to prevent dissonance. It seems possible that Tokyo / Vermont Counterpoint could be produced directly from this tool if the latter were extended further in time.
A more interesting challenge would be to create a devolution from the audio to tonematrix form. I claim such reverse engineering, followed by a Fourier transform to draw out the particular periodicities in frequency and time, can be used to generate an infinte family of pleasant sounding meanderings of arbitrary length. I would also like to consider the possibility of randomly placing and removing structures on the map at different positions: most of the early random and fractal music was interesting but sounded very much like garbage, whereas by forcing tonality on the output, tonematrix minimises the potential for something awful.