Tritone substitution

F#7 may substitute for C7 because they both share E♮ and B♭/A♯ and due to voice leading considerations

In music, a tritone substitution is the chord substitution of a chord a tritone away from the original. It is the use in a chord progression of a V7 (dominant seventh chord) (major/minor seventh chord) that is three whole steps (a tritone: 6 semitones) away from the original V7; using simpler analytic music notation (in equal temperament) it is: replacing V7 for bV7/V = bII7. For example, D♭7 would be the tritone substitution for G7 while F would substitute for B, and G♭ for C. Tritone substitutions are also used in improvisation and are commonly used to create tension during a solo.

C7 followed quickly by the tritone it contains (E-B♭), its inversion (B♭-F♭), and then G♭7 Play (help·info)

The reason these dominant seventh chords may be substituted for each other is that they share the two pitches that form a tritone in each chord (the third and seventh, albeit reversed). In a G7 chord, the third is B and the seventh is F. In the D♭7 chord, the third is an F and the seventh is C♭ (enharmonically B). Note that the interval between the third and seventh of a dominant seventh chord is itself a tritone.

One of the most common usages of the tritone substitution is in the 12 bar blues. Two 12 bar blues patterns appear below. The first is one of the simpler forms of 12 bar blues. The second shows the chord progression with a tritone substitution in measure 4. The tritone substitution is one of the most common substitutions found in jazz and was the precursor to more complex substitution patterns like Coltrane changes.

The 12-bar Blues and The Tritone Substitution

This is a representation of a simple 12-bar blues pattern in 4/4 time:

  I      IV     I      I      IV     IV       I       I       V       IV      I       I
| C    | F    | C    | C    | F    | F      | C     | C     | G     | F     | C     | C     |

The following is the same 12-bars incorporating a tritone substitution (sub V) in measure 4; that is, the Gb7, which is three whole tones away the root, C:

  I      IV     I      I  bV7   IV     IV       I       I       V       IV      I       I
| C    | F    | C    | C  Gb7 | F    | F      | C     | C     | G     | F     | C     | C     |

ii-V-I turnaround in C Play turnaround without tritone substitution (help·info)

The second common usage of the tritone substitution is in ii V I progressions. This substitution is particularly suitable for jazz because it produces chromatic root movement when applied to the ii-V-I progression that forms a basis of jazz harmony. For example, in the progression Dm7 - G7 - Cmaj7, substituting D♭7 for G7 produces the downward movement D - D♭ - C in the roots of the chords, typically played by the bass. This also reinforces the downward movement of the thirds and sevenths of the chords in the progression (in this case, F/C to F/B to E/B).

Tritone substitution ii-subV-I in C Play turnaround with tritone substitution (help·info)

Tritone substitutions are also closely related to the alt chord used commonly in jazz. The alt chord is a heavily altered dominant seventh chord, built on the alt scale that includes a flat ninth, sharp ninth, flat fifth, sharp fifth, and flat seventh. For example, C7alt is built from the scale C, D♭, D♯, E, G♭, G♯, B♭. Enharmonically, this is almost the same as the scale for G♭7, which is the tritone substitute of C7: G♭ (=F♯), A♭, B♭, C♭, D♭, E♭ (=D♯), F♭ (=E). The only difference is C, which is the sharp eleventh of the G♭7 chord. Thus, the alt chord is equivalent to the tritone substitution with a sharp eleven alteration.

mm.11-12 of "April in Paris" melody with tritone substitution in ii7-V7-i progression making ii7-♭II7-i.^[1] Play (help·info)

The Tritone substitution primarily implies a Lydian ♭7, or Lydian Dominant Scale. In the Case of C7 to Bmaj7, the implied scale behind C7 would be C D E F♯ G A B♭. Because of this, the extensions of 9, ♯11 and 13 are all available while the ♯11 is where it shares with the Altered Scale.

Classical harmonic theory would notate the "substitute" as an augmented sixth chord on ♭2. The Augmented sixth chord can either be the It⁺⁶ enharmonic to a dominant 7th chord without the 5th, Gr⁺⁶, enharmonically equivalent to a dominant 7th chord with the 5th, or Fr⁺⁶ enharmonically equivalent to the Lydian Dominant without the 5th, all of which serve in a classical context as a substitute for the secondary dominant of V (Satyendra 2005, p.55).

Below is the original dominant-tonic progression, that progression with the tritone substitution, and the same progression with the substitution notated as an Italian augmented sixth chord:

Tritone substitutions are a common technique in jazz and were first used by musicians such as Duke Ellington, Art Tatum, Coleman Hawkins, Roy Eldridge and Benny Goodman. According to Walter Everett (2004, 209) they were pioneered in the 1940s by Dizzy Gillespie.

Tritone substitutions are also known as substitute dominants, or Sub-V (Sub-five) chords.

See also

• Coltrane changes

Bibliography

• DeVeaux, Scott (1997). The birth of bebop: A social and musical history, p.104-106. Berkeley: University of California Press.

Sources

• Everett, Walter (Autumn, 2004). "A Royal Scam: The Abstruse and Ironic Bop-Rock Harmony of Steely Dan", Music Theory Spectrum, Vol. 26, No. 2, pp. 201-235.
• Stein, Deborah (2005). Engaging Music: Essays in Music Analysis. New York: Oxford University Press. ISBN 0-19-517010-5.
• Satyendra, Ramon. "Analyzing the Unity within Contrast: Chick Corea's Starlight". Cited in Stein (2005).

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