Goertzel Algorithm - Original Publication (1958).pdf

The initial publication by Gerald Goertzel's article titled "An Algorithm for the Evaluation of Finite Trigonometric Series" published in The American Mathematical Monthly (Jan, 1958). The algorithm is/was used in DTMF and other technologies for its computational efficiency.

This text can be difficult to find and remains a viable alternative to FFTs (efficiency-wise) even today. While Gerald Goertzel owned more than a dozen patents for similar algorithms, this one was a gift.