Chord Substitution
Swap a chord for a more interesting one without breaking the progression. The five reliable moves — diatonic substitutes, the tritone sub, secondary dominants, relative/parallel swaps, and borrowed chords — and exactly when each one works.
What is chord substitution?
Chord substitution is the craft of replacing one chord in a progression with another that does the same job — or shares enough of the same notes — so the music still moves the way you intended. The harmonic direction is preserved; the colour, the bass line, and the voice leading change.
It is the single biggest reason the same handful of progressions can sound completely different from one style to the next. A pop song and a jazz reharmonization can both be built on I–vi–IV–V; the jazz version simply substitutes richer chords into the same skeleton. Learn the moves below and you can reharmonize almost anything.
Function is what you preserve
Every chord in a key plays one of three roles: tonic (home/rest), subdominant (moving away), or dominant (tension that wants to resolve). The safest substitutions swap a chord for another chord in the same functional family, because the ear hears the same role.
| Function | Chords | Shared tones | Why they swap |
|---|---|---|---|
| Tonic | I · iii · vi | two notes each | vi (the relative minor) and iii both share two tones with I, so either can stand in for "home" while shifting the colour. |
| Subdominant | IV · ii | two notes | ii is the most common substitute for IV — same pre-dominant pull, slightly more motion. The basis of turning IV–V into ii–V. |
| Dominant | V · vii° | the tritone | vii° contains the leading tone and the same tritone as V7, so it resolves to I with nearly the same tension. |
Roman numerals make this easy to talk about — if you are new to them, the Roman numerals guide explains every symbol used on this page.
1. Diatonic substitution
The gentlest move: replace a chord with another from the same key that shares its function. Because every note stays inside the scale, the result sounds natural — just recoloured.
- I → vi: the deceptive move. End on vi instead of I and "home" turns wistful.
- IV → ii: turns a plain IV–V into a ii–V, the most common reharmonization in all of jazz.
- V → vii°: keeps the leading-tone tension with a lighter, rootless feel.
In C major, the run C → F → G can become C → Dm → G with no notes outside the key — same shape, more motion in the middle.
2. The tritone substitution
The most famous chromatic sub. Replace a dominant 7th with another dominant 7th a tritone away. In C, swap G7 for D♭7. It works because both chords contain the same tritone — the notes B and F — the interval that creates all the tension and demands resolution to C.
The reward is the bass line. Instead of G leaping down to C, the bass slides D♭ → C by a single half step. Apply it to a ii–V–I and Dm7 – G7 – C becomes Dm7 – D♭7 – C, with a chromatic bass walking down to the tonic.
3. Secondary dominants as substitutions
A secondary dominant is the dominant chord of a chord other than the tonic — written V/ii, V/V, V/vi, and so on. Rather than approaching a diatonic chord plainly, you precede it with its own V to pull the ear forward.
In C, the chord D7 is V/V — it is the dominant of G. Inserting it (C → D7 → G) substitutes a quiet approach with a strong one. You are not leaving the progression; you are tonicizing the next chord for a beat. Chains of secondary dominants are how a turnaround gathers momentum.
4. Relative & parallel swaps
Relative substitution
Swap a chord for its relative — a major chord for the minor a third below, or vice versa. C major and A minor share two notes, so trading them keeps the harmony while flipping its mood. This is the I ↔ vi move, viewed from the key it suggests. See relative keys.
Parallel substitution
Swap a chord for its parallel — same root, opposite quality (C major ↔ C minor). Dropping a parallel-minor chord into a major key (or the reverse) is a bright-to-dark recolour over the same bass note, and the gateway to modal interchange below.
5. Modal interchange (borrowed chords)
Modal interchange — borrowing — substitutes a chord from the parallel key or mode for the diatonic one. The most common is borrowing from the parallel minor while in a major key.
- iv for IV: the borrowed minor subdominant — that aching IV-to-iv slide in countless ballads.
- ♭VII: borrowed from Mixolydian, the rock cadence B♭ → C in the key of C.
- ♭VI: a dramatic, cinematic lift borrowed from the parallel minor.
Borrowed chords add one chromatic note to an otherwise diatonic progression — just enough colour to surprise the ear without losing the key. Combined with the four moves above, modal interchange completes the substitution toolkit.
Frequently asked questions
What is chord substitution?
Chord substitution is replacing one chord in a progression with a different chord that serves the same harmonic function or shares enough notes to fit. The progression still "works" — it moves the same direction — but the colour, voice leading, or bass motion changes. It is how the same I–vi–IV–V skeleton can sound like a pop song or a jazz standard.
What is a tritone substitution?
A tritone substitution replaces a dominant 7th chord with another dominant 7th whose root is a tritone (three whole steps) away. In C, you swap G7 for D♭7. Both chords contain the same tritone — the notes B and F — so they resolve to C with the same tension. The payoff is a smooth chromatic bass line: instead of G → C, the bass walks D♭ → C by a half step.
Can any chord be substituted for another?
No. A good substitution shares the original chord's function or its key tones. Swapping a tonic chord for an unrelated dominant will derail the progression. The reliable substitutes are the ones grouped by function (tonic, subdominant, dominant), the tritone sub for dominants, secondary dominants that target the next chord, and borrowed chords from the parallel key.
What is the difference between a diatonic and a chromatic substitution?
A diatonic substitution stays inside the key — replacing IV with ii, or I with vi, using only the seven notes of the scale. A chromatic substitution brings in notes from outside the key: a tritone sub, a secondary dominant, or a borrowed chord from the parallel minor. Diatonic subs change the colour subtly; chromatic subs add tension and surprise.
How do secondary dominants work as substitutions?
A secondary dominant is the V chord of a chord other than the tonic — written V/ii, V/V, and so on. Instead of moving straight to a diatonic chord, you precede it with its own dominant: in C, D7 (V/V) leads into G. It substitutes a plain approach with a stronger, pull-forward approach, adding momentum without leaving the progression.
Where do I hear chord substitution in real music?
Everywhere jazz reharmonizes a standard, and constantly in pop and gospel. A ii–V replacing a single IV, a tritone sub setting up the last chord of a turnaround, and borrowed iv chords in major-key ballads are all routine. Once you know the moves, you start hearing the same simple progressions dressed in different chords.