Diatonic Triad Harmony
View the degrees of the major scale as roots of triads, so you can build them from any position. This connects harmony to melody and lets you find progressions in any key.
Why
Every degree of a key carries its own triad. Knowing which triad belongs to each degree, and how it sounds, lets you build progressions intentionally
Seeing the scale as both a melodic and a harmonic framework strengthens your playing