Theory and Harmony Harmony: Major Scale and Scale Degrees Harmony the Chords of the Major Scale Harmony: The Minor Scale Harmony: Minor Key: V/vi Common in pop songs Harmony: Interchange in Mode Harmony: Circle of Fifths, Flat Seventh Chords Harmony: Diminished Triads, Secondary Dominants, Chromaticism. Harmony: Modes Harmony: Modern Serious Music, Jazz