Rob based his piece on the web of the spider Araneus diademus. He made use both of the structure and of a related scenario in which an insect is caught in the web and attacked by the spider. The repeating cylces of 13 pitches (a 12-tone set with the first repeated) represent the radii of the web, while the increasing tempo represents movement toward the center. Since it's the non-narrative aspects of the piece I admire, I'll leave the rest of the scenario to your imagination.