Definition
In tonal harmony not all chord successions have the same effect. What matters is how far the root moves from one chord to the next. Classifying these movements lets us understand why some progressions sound “natural” and directional, while others seem to go backward.
The three strong motions
| Root motion | Examples in C | Effect |
|---|---|---|
| Descending fifth (= ascending fourth) | V–I, ii–V, vi–ii, iii–vi, I–IV | the strongest: the root of the first chord becomes the fifth of the second |
| Descending third | I–vi, vi–IV, IV–ii | soft: two common tones, the new chord “colors” the previous one |
| Ascending second | IV–V, V–vi, ii–iii | dynamic: no common tones, strong sense of forward motion |
The weak motions (retrogressions)
- Ascending fifth (V–ii, I–V aside): the root of the second chord was already in the first as its fifth; the effect is one of return.
- Ascending third (I–iii, vi–I): often sounds like a “reinforcement” of the same chord.
- Descending second (V–IV, vi–V): typical of blues and rock, rare in the Classical style.
Retrogressions are not mistakes: they are simply less directional. In pop and rock (V–IV–I) they are part of the language.
The table of usual successions (Classical style, major mode)
| Chord | Usually goes to | Sometimes to | More rarely to |
|---|---|---|---|
| I | IV or V | vi | ii, iii |
| ii | V | IV, vi | I, iii |
| iii | vi | IV | I, ii, V |
| IV | V | I, ii | iii, vi |
| V | I | IV, vi | ii, iii |
| vi | ii or V | iii, IV | I |
| vii° | iii | I | — |
The I is a special case: it can go to any chord, because it is the starting point of every phrase. In practice the vii° is almost always used as an incomplete dominant (vii°6 → I).
The functional path
In summary: tonic → predominant (ii, IV) → dominant (V, vii°) → tonic. The vi and iii serve as linking chords: the vi leads to the predominants, the iii to the vi or the IV.
Practical rules
- For a phrase with a clear direction, use mainly descending fifths and ascending seconds toward the cadence.
- Use descending thirds to prolong a function without changing it (I–vi, IV–ii).
- The V–IV succession is to be avoided in the Classical style, but works perfectly well in a rock or blues piece.
- A long chain of descending fifths (vi–ii–V–I and beyond) is the basis of sequences by fifths.
Common mistakes
- Thinking any chord can go to any other “because it sounds good”: in the Classical tonal style direction matters.
- Using the iii as a predominant chord (iii–V): it sounds weak and ambiguous.
- Inverting the function: dominant before predominant (V–ii–I), which weakens the cadence.
Examples
- Gloria Gaynor, “I Will Survive”: Am–Dm–G–C–F–Bø–E, a chain of diatonic descending fifths.
- Pachelbel's Canon: D–A–Bm–F#m–G–D–G–A alternates descending fourths (that is, ascending fifths, a weak motion) and ascending seconds, which restore the forward drive.
- Bach chorales: almost every phrase ends with a ii6–V–I or IV–V–I succession.
- Blues: the V–IV–I turn is a deliberate retrogression that gives the genre its flavor.
How to use it in composition
- When a progression feels “flat,” check the root motions: the cause is often an excess of retrogressions.
- For a chorus that needs to push, use roots that rise by step (IV–V–vi) or fall by fifth (ii–V–I).
- For a suspended, modal atmosphere, deliberately use ascending thirds and descending seconds.
Exercise
- Write three eight-chord progressions in G major using only descending fifths and ascending seconds.
- Take a pop progression you know and classify each root motion.
- Rewrite a progression full of retrogressions to make it more directional, changing only two chords.
Connections
Diatonic functions: tonic, subdominant, dominant; Harmonic sequences and progression by fifths; Connecting root-position triads; Cadences; Pop progressions and loops.