**Atonality**

(...) but the most important contribution of *The Structure of Atonal Music* (Yale University Press, 1973) is the three pages that form Appendix I: Prime Forms and Vectors of Pitch-Class Sets, which is the clearest formulation we have of all the possible chords one can construct with the equal tempered chromatic scale. Here Forte went beyond musicology and looked at the chromatic scale as a mathematical entity of the numbers 0 to 114.
Twelve-tone theorists studied these possibilities a lot, but not until Forte’s book were the harmonic possibilities of the chromatic scale thoroughly examined. (...)

[Allen Forte]