There are three methods of computing Forte number and prime form.
Allen Forte published the first in his 1973 book The Structure of Atonal Music, citing a 1961 article by Milton Babbitt.
Forte packs from the left and Rahn packs from the right ("making the small numbers smaller" versus making "the larger numbers smaller").
[3] Programmers tend to prefer Rahn's method, because the Rahn prime is easily computed by comparing sets in binary, whereas Forte's prime requires a more complex algorithm.
[4] This United States musical biography article is a stub.