Jazz Reharmonization and Analysis

Core Idea

Reharmonization replaces chord progressions with substitute chords that preserve the melody while altering harmonic function and color. Substitutions maintain voice-leading smoothness or harmonic function. Analyzing reharmonization reveals jazz musicians' sophisticated harmonic thinking.

How It's Best Learned

Transcribe solo piano recordings (Bill Evans, Keith Jarrett) to analyze reharmonization choices. Compare original lead sheets with actual chord voicings to understand when substitutions preserve function versus transform meaning.

Common Misconceptions

• Assuming reharmonization is arbitrary or decorative; substitutions serve functional, voice-leading, or timbral purposes. - Confusing reharmonization with transposition or key change; reharmonization preserves melody and temporal grid. - Overlooking that reharmonization is improvisational and performance-specific.

Explainer

You already know jazz chord symbols and the basic harmonic vocabulary: ii–V–I progressions, dominant seventh chords, extended harmony. Reharmonization is the art of replacing the expected chord progression with a different set of chords that still works with the melody — and analyzing it means asking *why* a substitution works, not just noting *that* it occurred. The melody is the fixed element; the harmony beneath it is the variable. As long as the new chord contains the melody note or accepts it as a recognized tension, the substitution is technically valid. The creative judgment lies in choosing substitutions with interesting voice-leading, tonal color, or expressive effect.

The most fundamental substitution is tritone substitution: replacing a dominant seventh chord with the dominant seventh chord whose root is a tritone away. The G7 chord (G–B–D–F) shares its defining tritone (B–F) with D♭7 (D♭–F–A♭–C♭) — the tritone simply swaps positions between the two chords. Because the tritone is the interval that drives dominant chords to resolve, these two chords are functionally interchangeable. But where G7 resolves outward by a fifth, D♭7 resolves inward by a half step — creating chromatic bass motion instead of the expected root-motion by fifth. Bill Evans and Herbie Hancock use this substitution to create descending half-step bass lines that give familiar progressions a much denser chromatic texture.

Chord quality substitution and chord scale substitution work at a deeper level. Replacing a major chord with its parallel minor (or swapping a II chord for a ♭II chord) shifts color while preserving harmonic function. In chord scale substitution, the entire tonal region changes: a section originally implying Dorian mode might be reharmonized over a Lydian sound, shifting the tonal center while the melody notes — now reinterpreted as different chord tones or tensions — still fit. The melody note E, which was the ninth over D minor, becomes the major seventh over F major: the same pitch, radically different harmonic meaning.

To analyze reharmonization rigorously, transcribe both the original lead-sheet version and the performed version, then align them measure by measure. For each substitution, ask four questions: (1) Does the melody note work as a chord tone or accepted tension in the new chord? (2) Does the bass motion make sense — step, fifth, or tritone? (3) Is the harmonic rhythm preserved? (4) What tonal center or mode does the substitution imply? This framework converts impressionistic observations ("that sounds cool") into analytical claims ("this is a tritone substitution creating descending half-step bass motion across the bar line"), which is the difference between hearing jazz harmony and understanding it.