Questions: Jazz Reharmonization and Substitution in Composition
5 questions to test your understanding
Score: 0 / 5
Question 1 Multiple Choice
A composer wants to replace G7 → Cmaj7 with a tritone substitution. Which chord replaces G7, and what is the harmonic reason it works?
AF7 — it lies a whole step below the target and creates smooth voice-leading
BAb7 — it is built on the relative minor of C and shares several chord tones
CDb7 — it shares the tritone interval (notes B and F) with G7, so the harmonic tension is preserved and the bass descends chromatically into C
DE7 — it is the dominant of the parallel minor and creates chromatic color
The tritone substitution works because Db7 and G7 share the same tritone: the note B is the major third of G7 and the enharmonic minor seventh (Cb) of Db7; F is the minor seventh of G7 and the major third of Db7. These two notes carry the harmonic tension of the dominant chord. Because they appear in both chords, a melody note functioning over G7 will typically still function over Db7. Additionally, the bass moves Db → C (a half step down), creating smoother chromatic voice-leading than the G → C root movement by fifth.
Question 2 Multiple Choice
A student reharmonizes a 32-bar jazz standard by replacing every dominant chord with a tritone substitute and preceding each with a related ii–V insertion. Why might this approach undermine the musical effect?
ATritone substitutes clash with the melody when used more than twice in a row
BRelated ii–V insertions are only valid before ii–V–I progressions, not before individual dominants
CHarmonic saturation exhausts the listener's ear — constant substitution removes the tonal landmarks that give reharmonization its impact when used selectively
DUsing tritone substitutes on every chord violates standard voice-leading rules by creating parallel tritones
Reharmonization is most effective when used selectively: at a repeated phrase that needs freshening, a cadence that wants delay, or a climactic moment. When every chord is substituted, there are no simple reference points left for the ear to orient against. The sophistication of the substitution is perceived only in contrast to simpler harmonies. Constant substitution also fatigues the ear and can obscure the melodic line. The craft is knowing which moments to leave alone.
Question 3 True / False
When replacing G7 with its tritone substitute Db7, the tritone interval B–F appears in both chords (as different chord tones), which is why melody notes that work over G7 tend to also work over Db7.
TTrue
FFalse
Answer: True
In G7, B is the major third and F is the minor seventh. In Db7, F is the major third and B (= Cb enharmonically) is the minor seventh — the roles are swapped, but the interval is preserved. Since these two notes carry the harmonic identity and tension of the dominant chord, a melody note that functions as a chord tone or usable tension over G7 will typically function similarly over Db7. This shared tritone content is the entire mechanical basis for why the substitution preserves harmonic integrity.
Question 4 True / False
Because tritone substitutes preserve melodic integrity through shared chord tones, they can be applied uniformly to most dominant chord in a progression for maximum harmonic sophistication.
TTrue
FFalse
Answer: False
Selective use is the essence of the craft. Reharmonization succeeds when it provides contrast — freshening a repeated phrase, coloring a climax, delaying a cadence — precisely because simpler harmonies elsewhere give the ear reference points. Applying substitutions uniformly removes this contrast effect, creates harmonic saturation, and may obscure the melody. The decision of *where* to substitute is as important as knowing *how* to substitute.
Question 5 Short Answer
Explain why tritone substitution preserves the harmonic tension of the original dominant chord, using the structure of the two chords involved.
Think about your answer, then reveal below.
Model answer: A dominant seventh chord's tension comes from its tritone interval — the third and seventh of the chord form an interval of three whole steps (a tritone) that creates strong harmonic instability resolving to the tonic. G7's tritone is B–F. The tritone substitute Db7 contains the same tritone: F is now the third of Db7 and B (Cb) is the seventh. Because both chords share this tritone, they carry the same essential harmonic tension and both resolve convincingly to Cmaj7, just via different bass motion (G→C by fifth vs. Db→C by half step).
The shared tritone is the entire basis of the substitution. Without it, replacing G7 with an arbitrary dominant would work only by coincidence. Understanding *why* the substitution works (not just *which* chord to use) lets you extend the principle: any time two dominant chords share a tritone, they are interchangeable as tension-bearers, and you can choose based on bass line, voice-leading economy, or melodic fit.