Pitch Class Sets
These are pdf's of all pitch-class sets. Here and here you will find introductions, albeit somewhat detailed, to the topic, and here an online set calculator. While the concept of pitch-class sets was initially introduced to be used as an analytical tool, notions associated with pitch-class sets can have useful compositional applications. Allen Forte first coined the term, though others, particularly Howard Hanson, had done previously done important work in the area. Refer to Hanson's seminal 1960 work Harmonic Materials of Modern Music.