Prerequisites for Jazz Tritone Substitution Success

What is the functional role of the dominant seventh chord in traditional harmony?

The dominant seventh chord functions as the primary engine of harmonic tension, demanding resolution to a tonic chord by establishing a clear hierarchy of tonal gravity.

• Tension: The tritone interval between the third and seventh degrees creates an inherent instability that pulls the ear toward a point of rest.
• Resolution: The leading tone of the dominant chord typically resolves upward by a half-step to the tonic root.
• Direction: The seventh of the chord resolves downward by a half-step to the third of the tonic chord.
• Hierarchy: This relationship defines the V7-I cadence, which serves as the fundamental structural pillar in Western functional harmony.

How do secondary dominants establish temporary tonal centers?

Secondary dominants establish temporary tonal centers by acting as the V7 chord for a non-tonic scale degree. For example, playing an A7 to resolve to Dm creates a momentary pull toward the ii chord in the key of C, effectively tonicizing it for the duration of the progression.

What is the mathematical relationship between a tritone interval and the circle of fifths?

The tritone is the interval of six semitones that splits the octave exactly in half, placing it at the polar opposite position of any note on the circle of fifths. Many players assume the tritone is a dissonant anomaly that exists outside the circle, but it is actually a precise geometric mirror. If you move six steps clockwise or counter-clockwise from any root on the circle, you arrive at its tritone. This mathematical symmetry is exactly why the substitution works so effectively; the two chords share the same functional guide tones.

How does the voice leading of a flat-five substitution resolve into a tonic chord?

In a flat-five substitution, the dominant chord's third and seventh are inverted to become the seventh and third of the substitute chord. For instance, in a G7 chord, the B and F notes create the tritone. When you play a Db7, the F acts as the third and the Cb—which is enharmonically B—acts as the seventh. This shared tritone allows the substitute chord to resolve to the tonic with the same voice-leading efficiency as the original V7.

A common nuance involves the quality of the tonic chord. While this substitution resolves perfectly to a major tonic, resolving to a minor tonic often requires the use of a Lydian dominant scale over the substitute chord to avoid clashing with the natural sixth of the minor scale. This adjustment maintains the intended harmonic color while satisfying the ear's expectation for a smooth, chromatic resolution.

What are the defining characteristics of a V7-I cadence in major and minor keys?

A V7-I cadence relies on the resolution of the leading tone to the tonic, usually involving a half-step move. In a major key, the V7 contains a major third, while in a minor key, the V7 typically utilizes a raised third to create the necessary leading tone.

How do chord extensions and alterations change the harmonic color of a dominant seventh chord?

Extensions like the 9th, 11th, and 13th add vertical density to a chord, while alterations like the b9, #9, #11, or b13 introduce chromatic tension that pushes the harmony further away from the tonic. These additions change the chord's color by introducing notes outside the standard diatonic scale, which forces the ear to anticipate a stronger resolution. A G7(b9, b13) creates a darker, more urgent sound than a standard G7, often signaling a shift toward a minor key.

One notable exception is the use of the #11 extension on a dominant chord. When applied to a substitute dominant, the #11 is actually a consonant note within the scale of the tonic, which can soften the expected tension. This creates a more stable, "Lydian" sound that is less prone to demanding an immediate, aggressive resolution compared to a standard altered dominant chord.

What is the difference between a diatonic chord and a chromatic substitute?

Diatonic chords are built strictly from the notes of a given scale, whereas chromatic substitutes introduce notes from outside that scale to create harmonic variety.

Use these percentage estimates to gauge how much tension you are introducing into a progression; the lower the percentage, the more chromatic color you add.

How does the concept of root movement by half-step impact jazz improvisation?

Root movement by half-step creates a smooth, linear bass line that minimizes the physical distance the hand must travel while maximizing the sense of harmonic surprise.

• Chromaticism: This movement forces the listener to accept new tonal centers rapidly, which is a hallmark of modern jazz improvisation.
• Efficiency: The short distance between roots allows for faster execution during complex bebop heads or rapid-fire soloing.
• Voice-leading: Moving by half-step creates a natural "slide" effect that connects chord tones with minimal angularity.
• Color: This technique allows the soloist to bypass traditional diatonic expectations, creating a more sophisticated and modern sound.