Back in the 1950's and 60's, once the beginner on a spinet home organ reached a certain level with one of the easy play methods such as the Pointer System [See blog, "Easy Play" Methods], they were typically eager and ready to explore the subject of harmony.
For taking these beginners to the next level, some teachers liked to turn to Orem's Harmony (photo).
This is an old textbook and writing book for the first year's work that was first published in 1916, for class, private, or self instruction.
It included the study of scales, intervals, common chords, the dominant 7th chord, and melody making.
Preston Ware Orem (1865-1938) was an American composer, pianist, and writer of music who, while he worked as an organist, teacher, music critic, editor, choral conductor, composer, and author of numerous musical transcriptions and arrangements, is chiefly remembered today for being a writer of theory books, including his "Harmony for Beginners" and 9 books of exercises.
Using Orem's Harmony book, the student would work his assignment in pencil and bring it to his lessons, where his instructor would review and correct, if necessary, any errors.
If you worked your way gradually through this entire book under the supervision of a good teacher without skipping anything, it was worth every minute, it prepared you for the more in depth look at popular and classic organ music which was certain to follow, and would even make the first year's work in a college level musical program much easier.