The 'Magic Number' of Jazz Harmony: Unlocking the Fretboard with the Diatonic Circle of Fifths

The II–V–I progression is everywhere in jazz—but why? This post uncovers the deeper logic behind it: the Diatonic Circle of Fifths (7–3–6–2–5–1–4). Discover how this “magic number” explains the flow of harmony in tunes like Fly Me to the Moon and Autumn Leaves, and how it transforms your view of the fretboard through the Functional Diagonal Approach.