Reharmonization

Reharmonization is what happens when you take a melody you know cold and put new chords underneath it — chords the original composer never wrote. It exists because a melody note is rarely locked to just one harmony; the same note can be the root of one chord, the 3rd of another, the 9th of a third, and each choice paints the tune in a different light. Every jazz musician who “makes a standard their own” is doing this, and the whole art of it comes down to one constraint: the melody has to still make sense.

The one rule everything else obeys

The melody is the anchor. Whatever chord you substitute in, the melody note landing on it needs to be a chord tone or an available tension of the new chord, not a clash — a sustained C in the tune cannot sit under an EMaj7, because that chord (E–G♯–B–D♯) contains no C and none of its usable color tones (F♯, A♯, C♯) is a C either. This is why reharmonizing always starts with the same question: for this melody note, what could the chord underneath actually be — its root, 3rd, 5th, 7th, or a color tone like a 9th or 13th? Dominant chords are the most forgiving harmony to reharmonize with, since between chord tones and altered alterations a single V7 can support most of the twelve notes in the octave; a plain major triad supports far fewer. This whole approach is really the mirror image of harmonizing a melody from scratch — instead of building the first set of chords, you’re asking what other chords could also carry the same tune.

The core toolbox

Most reharmonization is built from a handful of moves, used alone or stacked together.

• Tritone Substitution: swap a dominant chord for the dominant a tritone away — G7 becomes D♭7 — because they share the same 3rd and 7th, so the harmony barely disturbs the melody while the bass now falls chromatically instead of jumping a fourth.
• Modal Interchange: borrow a chord from the parallel minor (or another mode of the same tonic), darkening a major-key passage without leaving the key center — this is how the backdoor ii–V (♭VII7 resolving to I) gets its distinctive sound.
• Adding or extending ii–Vs: stretch a single resolution into a chain of ii–Vs, or insert a secondary dominant in front of a diatonic chord to give it its own pull — a favorite move on Turnarounds.
• Passing Diminished Chords: fill the gap between two diatonic chords a whole step apart with a diminished seventh built a half step below the second chord, creating stepwise, chromatic bass motion.
• Chord-quality change: turn a static ii–V into something sharper by altering the quality of a chord in place — a minor 7th becomes half-diminished, a major 7th becomes dominant — which is a lighter cousin of full modal interchange.
• Constant Structure: move the same chord type (say, a dominant 7 shape) in parallel through several roots, ignoring the underlying key center entirely for a stretch of bars.

Underneath all of it, Voice Leading is what separates a reharmonization that sounds inevitable from one that sounds like a wrong note — the smoother the 3rds and 7ths move between chords, the more convincing the substitution.

Coltrane changes: reharmonization as a whole system

The most extreme, systematized version of this idea is Coltrane Changes, where a single ii–V–I gets exploded into three major-third-related key centers, each one approached by its own dominant — a symmetrical scheme that treats functional harmony almost like a geometric grid instead of a single tonal center. It’s worth studying as the far end of the spectrum: the same governing rule (melody note dictates chord options) pushed until the original tune’s harmonic identity nearly dissolves into pure key-center motion.

Reharmonizing the same phrase three ways

Start with a plain ii–V–I in C:

• Original: Dm7 – G7 – CMaj7

Tritone substitution replaces the V7 and creates a chromatic bass line into the tonic:

• Reharmonized: Dm7 – D♭7 – CMaj7

Notice the bass motion: G7 falls a fourth into C, while D♭7 falls only a half step:

Coltrane-style substitution takes a simple ii–V–I (here in E♭) and threads it through two extra key centers — B and G, a full major-third cycle back to E♭ — before landing:

• Original: Fm7 – B♭7 – E♭Maj7
• Reharmonized: Fm7 – G♭7 – BMaj7 – D7 – GMaj7 – B♭7 – E♭Maj7

Modal interchange darkens a I–IV–I phrase in F by borrowing the iv chord from F minor:

• Original: FMaj7 – B♭Maj7 – FMaj7
• Reharmonized: FMaj7 – B♭m7 – FMaj7

♫ Listen

• Bill Evans Trio — “Autumn Leaves” (Portrait in Jazz, 1959): listen to how Evans recolors the familiar changes through the head — substitute chords and fresh inner voices under a melody everyone knows, a study in reharmonizing without losing the tune’s shape.
• Herbie Hancock — “'Round Midnight” (film score, 1986): Hancock elongates and reharmonizes Monk’s own tune, swapping in contemporary inversions and non-root-position voicings that keep the melody’s late-night mood intact while completely updating the harmonic language underneath it.
• Keith Jarrett Trio — “All the Things You Are” (Tokyo, 1996): listen for rootless and drop-2 substitutions layered onto Jerome Kern’s well-worn changes — proof that even a standard this familiar still has fresh chords hiding under its melody.

Related: Chord Substitution, Tritone Substitution, Modal Interchange, Coltrane Changes, Harmonizing a Melody, Constant Structure