PROGRESSION · I–III–IV–iv
The Minor Plagal Turn
Ordinary major harmony that turns at the last moment, when IV becomes minor. Also called the borrowed iv, or the minor four.
In C major
C – E – F – Fm — aching, resigned, unmistakably sad, around 84 BPM.
Why it works
The move is a single note: the sixth degree of the key drops a semitone as IV becomes iv. That flattened sixth is borrowed from the parallel minor, and it is one of the most reliable sadness levers in tonal music — the chord is still built on the same root, so the ear registers a change of colour rather than a change of place. The III major before it sharpens the effect by first raising a note the key does not have, so the loop swings from brighter-than-expected to darker-than-expected.
Where you'll hear it
Ballad choruses and last-chorus variations. Take a progression the listener has already heard four times and make only the IV minor; it lands every time.
I–III–IV–iv in every key
The same progression transposed. The roman numerals never change — that is the whole point of writing progressions this way.
| Key | I | III | IV | iv |
|---|---|---|---|---|
| C | C | E | F | Fm |
| Db | Db | F | Gb | Gbm |
| D | D | F# | G | Gm |
| Eb | Eb | G | Ab | Abm |
| E | E | G# | A | Am |
| F | F | A | Bb | Bbm |
| F# | F# | A# | B | Bm |
| G | G | B | C | Cm |
| Ab | Ab | C | Db | Dbm |
| A | A | C# | D | Dm |
| Bb | Bb | D | Eb | Ebm |
| B | B | D# | E | Em |
Related progressions
Drill the chords behind I–III–IV–iv
Build every chord in this progression from its symbol, against the clock.
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