In the 300-pg course, “The Secrets To Playing Piano By Ear,” we cover the diatonic chords of every major scale. Don’t worry if you don’t know what “diatonic” means — it’s just a fancy way of saying “pertaining to the major or minor scale,” the most common of all scales. Each major key has a set of diatonic chords that naturally occur on each tone of the scale. To figure out these chords, just…