In tonal music theory, diatonic chord quality is determined by constructing triads strictly upon each scale degree within a defined key signature to ensure all notes belong to that specific mode. The governing rule dictates that major keys inherently contain three major chords (scale degrees 1, 4, and 5), one diminished chord at scale degree 7, and minor chords filling the remaining positions, while natural minor keys shift this configuration so that scales 1, 4, and 5 form a relative harmonic minor structure with two being diminished. This structural mapping establishes the necessary vertical harmony required for functional progression within the constraints of common-practice tonal systems without invoking borrowed notes or altered extensions outside the key's diatonic collection.
In tonal music theory, diatonic chord quality is determined by constructing triads strictly upon each scale degree within a defined key signature to ensure all notes belong to that specific mode. The…