This is hopelessly geeky stuff, but if you’ve been messing with it for decades like I have, it is just so cool to have a concise history of how the Just diatonic scale is built: Just Intonation For dulcimer fretting, the KEY is to remember that the open string is scale degree 5, and not 1 like most people expect. The 3rd fret is 1 or “do” !!!