Modal Harmony

Unit 2 treated the seven church modes as scales, and the question there was which note you start the white keys from.

This lesson is about harmony: why sounding chords over a mode requires a different way of moving than functional harmony does.

Two driving principles

Functional harmony moves by tension and resolution. Leave the tonic, reach maximum tension on the dominant, return to the tonic. As Unit 4 established, that round trip is the source of momentum.

Modal harmony does not use it. It sustains music instead by holding the color of one mode.

	Functional harmony	Modal harmony
Driven by	the round trip of tension and resolution	persistence of modal color
Tonic established by	the leading tone of the dominant	repetition, drones, metrical placement
Chord progression	has direction	coloring more than direction
Avoids	parallel fifths and the like	creating a leading tone

The last row is the consequential one. Modal harmony avoids creating a leading tone.

The reason is simple: with a leading tone present, the ear insists on hearing major or minor. Sound a G7 over C Dorian and the listener picks up the B and concludes “C major” or “the V of C minor.” Dorian’s characteristic tone, A, becomes a passing detail inside that interpretation.

Foregrounding the characteristic tone

Making a mode audible as that mode requires putting forward the note that differentiates it from its neighbors — the characteristic tone.

Mode	Compared against	Characteristic tone	On C
Dorian	natural minor	sixth degree (♮6)	A
Phrygian	natural minor	second degree (♭2)	Db
Lydian	major	fourth degree (♯4)	F#
Mixolydian	major	seventh degree (♭7)	Bb

The most reliable way to foreground a characteristic tone is to alternate the tonic with a chord containing it.

Building a triad on the fourth degree of C Dorian gives F A C, a major triad. In natural minor the A would be Ab, making it Fm.

So alternating Cm and F is enough to establish Dorian, because IV being major is itself the act of sounding the characteristic tone A.

i – iv against i – IV

▶Natural minor (i – iv)▶Dorian (i – IV)

Check: Both are minor-type sonorities on C. The first has a minor iv (Fm), which is ordinary natural minor. The second has a major IV (F), which is Dorian. The difference is one note, Ab against A, and the second admits a strange brightness into the darkness. That suspended brightness is what Dorian is.

Cm – Fm – Cm

Check

The characteristic tone of C Lydian is F#. Which chord sounds it most directly?

FmG7Cmaj7D (major triad)

Check answer

Mixolydian and ♭VII

The most used major-type mode is Mixolydian: on C, C D E F G A B♭. Its only difference from the major scale is the seventh degree.

That single change carries a great deal. The leading tone disappears. With B becoming B♭ there is no longer a note a half step below the tonic, so the pull from dominant to tonic stops operating.

A triad on the seventh degree gives B♭ D F, the major triad ♭VII.

Unit 8 treated this ♭VII as a borrowed chord — a chord imported into C major from the parallel minor. A second account is available here: a diatonic chord of Mixolydian on C.

Which is correct depends on context. If the piece is mostly in C major and B♭ appears for an instant, it is borrowing. If B never appears anywhere in the piece, it is no longer a major key at all; it is Mixolydian.

A progression using V, and one using ♭VII

▶Functional (I – IV – V – I)▶Mixolydian (I – ♭VII – IV – I)

Check: The first passes through the dominant G. The B sounds, the leading tone operates, and arriving at C feels like resolution. The second passes through Bb instead. With no leading tone the sense of resolution is faint, and what you get instead is a change of color and a return. Both end on C, and C means something different in each.

the leading tone B operates

A seventh on the tonic chord — I7

Stacking four notes in thirds on the tonic of Mixolydian gives C E G B♭, which is C7. The shape is a dominant seventh exactly.

Unit 8 held that hearing a dominant seventh nearly determines the tonic chord that follows. That does not happen here. A dominant seventh has drive because its seventh and tritone point at a destination, and that destination is fixed by the leading tone rising to the tonic. Mixolydian has no leading tone, so the B♭ of C7 points nowhere. The chord is a dominant seventh in shape and a tonic in function.

Unit 8 mentioned the shape of a seventh sitting on the tonic in connection with secondary dominants (V7/IV). The I7 of blues and rock is the same chord, but it stays put rather than moving to IV. Once it stays, it is not a secondary dominant but a modal tonic. Which is why analyzing the I7 in the first measure of a twelve-bar blues as a secondary dominant of IV explains nothing — the IV it supposedly points to never arrives.

Check

Stacking a four-note chord on the tonic of C Mixolydian gives C7. Why does that C7 not function as a dominant seventh?

The scale has no leading tone, so the seventh has no fixed destinationThe fifth has been loweredIt is not in root positionThe seventh is not a minor 7th

Check answer

Tools for holding a mode

Making the tonic sound like the tonic without a leading tone requires other means.

1. A drone — sound the tonic continuously in the bass. It is the pedal point of Unit 6, with a stationary note creating a center
2. Repetition — alternate a short pair of chords. Sheer frequency communicates where the center is
3. Metrical placement — keep putting the tonic chord on the downbeat
4. Quartal voicings — stack in fourths rather than thirds, weakening the major/minor distinction and letting modal color come forward

None of these attracts by pull; each creates a center by remaining there. Where functional harmony speaks through motion, modal harmony speaks through staying.

The number of chords drops accordingly. Pieces that alternate two or three chords are common because the harmony has no obligation to advance a narrative. The narrative is carried by melody and rhythm, and the harmony maintains the color of the stage.

Check

Why do modal pieces often use so few chords?

A mode contains only three chordsThe harmony is not responsible for advancing a narrative; its job is to hold a colorComplex chords do not suit modesIt would be too difficult to perform

Check answer

▶ Check the characteristic tone of C Dorian in the mode dictionary The characteristic tone is highlighted on the keyboard. Switch between Dorian and Phrygian and observe that only one or two notes change Mode Dictionary →

Modal harmony creates color within the frame of a seven-note mode. The next lesson removes the assumption of seven notes altogether, taking up symmetrical scales built from repeating identical intervals.