Harmony
Reharmonization
Reharmonization means replacing or enriching the chords of a piece while keeping its melody, for example turning C Am F G into Cmaj7 A7 Dm7 G7.
What is reharmonization?
Reharmonizing means keeping the melody and changing what lies underneath. The same sung notes take on a new colour: jazzier, darker, more surprising. Arrangers do it every time they cover a standard, and you can do it on any chord progression.
There is only one constraint: every important melody note must stay compatible with the new chord. It should be a chord tone or an extension (9, 11, 13), and should avoid sitting a half step above a chord tone.
What are the main reharmonization techniques?
- Diatonic substitution: replace a chord with another of the same function. C becomes Am7 or Em7, F becomes Dm7.
- Enrichment: move to extended chords. C becomes Cmaj9, G becomes G13.
- Secondary dominants: put a V7 in front of a chord. Am becomes A7 to lead into Dm.
- Tritone substitution: G7 becomes D♭7, A7 becomes E♭7.
- Modal interchange: F becomes Fm, or you add A♭ and B♭.
Add passing diminished chords on top: C C#dim7 Dm7 (x3545x, x4535x, x5756x) fills the gap between I and ii with a chromatic bass.
Step-by-step example: reharmonizing C Am F G
Start from the pop progression C Am F G, one bar per chord, and go up one level at a time:
| Level | Progression | Technique |
|---|---|---|
| 0 | C Am F G | Original |
| 1 | Cmaj7 Am7 Fmaj7 G7 | Sevenths |
| 2 | Cmaj7 A7 Dm7 G7 | Secondary dominant, ii for IV |
| 3 | Cmaj7 E♭7 Dm7 D♭7 | Tritone substitutions |
Level 3 sits entirely on the 5th string: Cmaj7 x3545x, E♭7 x6868x, Dm7 x5756x, D♭7 x4646x, then back to Cmaj7. The bass goes C, E♭, D, D♭, C: a chromatic line that sounds instantly like jazz. Softer variant: Cmaj7 Am7 Fmaj7 Fm6, with the borrowed minor iv right before the tonic.
How to reharmonize without losing the melody
Play the melody on the 1st and 2nd strings and the chord on the lower strings. On every long note, ask yourself: is it in the new chord? If the melody holds an E during the Am bar, A7 works (E is its fifth), and so does E♭7 (E becomes a very tense ♭9, best kept for jazz).
Start small: one substitution per phrase, ideally on dominant bars or just before the return to the tonic. To test ideas fast, the AI progression analysis suggests reharmonizations for a progression you type in.
Key takeaways
- Reharmonizing = keep the melody, change the chords.
- Five tools: diatonic substitution, extensions, secondary dominants, tritone substitution, modal interchange.
- Check every long melody note against the new chord.
- One well-placed substitution beats ten random ones.
Frequently asked questions
What is the difference between reharmonization and chord substitution?
A substitution replaces one specific chord with another (G7 with D♭7). Reharmonization is the overall approach: it combines several substitutions to give a whole passage a new colour.
Where should I start when reharmonizing a song?
First add sevenths to every chord, then replace IV with ii (F with Dm7). Next, turn the chord before the ii into a secondary dominant (Am becomes A7). Those three steps alone change the character of a song.
Does reharmonization work in pop and folk?
Yes. A borrowed Fm before C, an E7 before Am or a B♭ before C is enough to make a ballad more moving without making it sound like jazz. Folk guitarists use these moves all the time in their covers.
Related terms
- Tritone substitution
- Secondary dominant
- Modal interchange (borrowed chords)
- Extended chords (9, 11, 13)
- Chord progression
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