joseph schillinger described an operation of "polynomial time multiplication" ("polynomial" refers to any rhythm consisting of more than one duration) corresponding roughly to that of pitch multiplication above ( ). a theme, reduced to a consistent series of integers representing the quarter, 8th-, or 16th-note duration of each of the notes of the theme, could be multiplied by itself or the series of another theme to produce a coherent and related variation. especially, a theme's series could be squared or cubed or taken to higher powers to produce a saturation of related material.