Using these 25 groups in conjunction with pitch multiplication, Boulez is able to create 25 "harmonic fields" within each set. Koblyakov in his analysis assigns a letter to each cluster within a set, such that two sets multiplied together can be notated as "aa," "bc," "ed," etc. . Boulez's form of pitch multiplication can be thought of more as pitch addition. With this technique, Boulez takes two clusters and takes the sum of every possible pairing between the two clusters. For example, if we were to multiply groups b and c within set I, we would have the following: