https://www.thegearpage.net/board/index.php?threads/music-theory-made-simple-0-index-toc.1371119
https://musictheory.pugetsound.edu/mt21c/HalfStepsAndWholeSteps.html
https://monoskop.org/images/d/da/Schoenberg_Arnold_Fundamentals_of_Musical_Composition_no_OCR.pdf

