Assignment 4 Results, page 1:

Rozalie Hirs' patch: This patch takes two pitches, and in the first omloop, builds a harmonic series for each pitch, ring modulates the results and then removes the duplicate results after quantizing to the nearest 1/8th tone. This process is done 12 times, each time increasing the number of partials for the harmonic series by one.

The subpatch labelled 'subtract common elements' compares each chord with the previous one, removing any common elements between them (the first chord is not compared of course).