I recently finished Dick Sudhalter’s book on early jazz. In the first part of the book, he refers to a standard text on harmony which was used in the 20s and 30s. Foolishly, I did not note the title. I now cannot find the reference in Sudhalter’s 700+ pages. Does anyone know what this text would be?

Gad, there are scores. Considering the time frame, maybe Hindemith's Elementary Training for Musicians.

Older (but not 20s-30s) standard texts are by Robert Ottman or Walter Piston.

A slightly different bent, but downloadable for free, is Berklee School of Music's Theory Course. <SCRIBD id="133215036"><LINK_TEXT text="https://www.scribd.com/doc/133215036/Be ... mony-1-pdf">https://www.scribd.com/doc/133215036/Berklee-College-Of-Music-Harmony-1-pdf</LINK_TEXT></SCRIBD>