Harmony and chord progressions

Build a chord on every note of a scale, using only notes from that scale, and you get the key's diatonic chords. Progressions are sequences of these chords. Roman numerals let you describe a progression in any key at once.

Diatonic chords and Roman numerals

Number the chords by the scale degree of their root. Uppercase numerals are major chords, lowercase are minor, ° is diminished, ø is half-diminished.

In minor keys, this course writes ♭III, ♭VI and ♭VII to show those roots are a semitone lower than in major. Many guides simply write III, VI and VII; they mean the same chords.

Function: home, away, tension

• Tonic (I, also vi and iii): home, rest.
• Subdominant (IV and ii): moving away, a gentle lift.
• Dominant (V and vii°): tension that wants to return home. A V7 chord contains a tritone between its 3rd and ♭7; when it moves to I, those two notes each slide a semitone into the tonic chord. That pull is the engine of cumbia harmony.

Cadences worth knowing

• V7 to I: the strongest return home. G7 to C.
• IV to I: softer, a churchy “amen”.
• The Andalusian cadence, i, ♭VII, ♭VI, V7: Am, G, F, E7. A stepwise fall with Spanish roots, everywhere in flamenco, Latin pop, chicha and digital cumbia.

How each genre uses harmony

• Dub and reggae: one or two chords looping for the whole tune, so the bass can be the melody. Common vamps: i–iv (Am–Dm), i–♭VII (Am–G), I–IV in major, and the Dorian vamp i–IV (Am–D), where the major IV gives a lifted, soulful feel. In dub mixes the chords are reduced to fragments and echoes.
• Dub techno and minimal: often a single chord for the whole track. m7, m9, m11 and sus chords. Movement comes from filters, delay and texture, not chord changes. A common trick is moving one chord shape in parallel (a “chord memory” shape transposed up or down) even when that leaves the scale.
• Cumbia: classic functional harmony. I–V7 back and forth, I–IV–V7–I, minor i–iv–V7–i using harmonic minor, and the Andalusian cadence. Dominant 7th chords are essential, and the bass alternates between each chord's root and 5th.