Editing Tritone substitution (section)

===Jazz / Pop===

[[File:Tritone substitution.png|thumb|right|F{{music|#}}<sup>7</sup> may substitute for C<sup>7</sup> because they both have E{{music|natural}} and B{{music|flat}}/A{{music|sharp}} and fulfill the [[voice leading]] considerations. {{audio|Tritone substitution.mid|Play}}]]

A tritone substitution is the substitution of one [[dominant seventh chord]] (possibly altered or extended) with another that is three [[whole step]]s (a [[tritone]]) from the original chord. In other words, tritone substitution involves replacing V<sup>7</sup> with {{music|b}}II<sup>7</sup><ref name="Sarath"/> (which could also be called {{music|b}}V<sup>7</sup>/V, subV<sup>7</sup>,<ref name="Sarath"/> or V<sup>7</sup>/{{music|b}}V<ref name="Sarath"/>). For example, D{{music|flat}}<sup>7</sup> is the tritone substitution for G<sup>7</sup>.

In standard [[jazz harmony]], tritone substitution works because the two chords share two pitches that themselves are a tritone apart: namely, the [[third (chord)|third]] and the [[seventh (chord)|seventh]] of the chord, albeit reversed.<ref>Freeman, Daniel E. (2009). ''The Art of Solo Bass'', p.17. {{ISBN|0-7866-0653-3}}.</ref> In a G<sup>7</sup> chord, the third is B and the seventh is F; in its tritone substitution, D{{music|flat}}<sup>7</sup>, the third is F and the seventh is C{{music|flat}} ([[enharmonic]]ally B{{music|natural}}).

[[File:Tritone substitution common tones.png|thumb|right|C<sup>7</sup> followed quickly by the tritone it contains (E-B{{music|flat}}), its inversion (B{{music|flat}}-F{{music|flat}}), and then G{{music|flat}}<sup>7</sup> {{Audio|Tritone substitution common tones.ogg|Play}}.]]

Edward Sarath calls tritone substitutions a "non-diatonic practice that is indirectly related to applied chord functions... yield[ing] an alternative melodic pathway in the [[Bass (sound)|bass]] to the [[tonic (music)|tonic]] triad."<ref name="Sarath">Sarath, Edward (2009). ''Music Theory Through Improvisation: A New Approach to Musicianship Training'', p.177. {{ISBN|0-415-80453-1}}.</ref> Patricia Julien says it involves replacing "harmonic root movement of a fifth with [[steps and skips|stepwise]] root movements (e.g., G<sup>7</sup>–C becomes D{{music|b}}<sup>7</sup>–C) so that although stepwise root movement is involved, the relationship between the chords is functional".<ref>Julien, Patricia (2001). ''Jazz Education Journal'', Volume 34, p.ix–xi.</ref>

The original dominant pitch (the sharp fourth, also called sharp eleventh or flat fifth, relative to the original root) is often added to the tritone substitute dominant, due to that note's importance melodically and tonally – this is one of the ways in which substitute dominants may sound and function somewhat differently than conventional dominant chords.<ref name="Ligon">Ligon, Bert (2001). ''Jazz Theory Resources'', p.128. {{ISBN|0-634-03861-3}}.</ref> (However, sharp elevenths can also occur on non-substituted dominant chords in jazz.) The substitute dominant may be used as a [[pivot chord]] in [[modulation (music)|modulation]].<ref>Bahha and Rollins (2005). ''Jazzology'', p.103. {{ISBN|0-634-08678-2}}.</ref> Since it is the dominant chord a tritone away, the substitute dominant may resolve down a fifth, to a tonic chord a tritone away from the previous tonic (for example, in F one may feature a ii–V on C, which with a substitute dominant resolves to G{{music|b}}, a [[distant key]] from F). Resolution from the substituted chord to the original tonic is also common.

Tritone substitutions are also closely related to the [[altered chord]] used commonly in jazz. [[Jerry Coker]] explains:

{{blockquote|Tritone substitutions and altered dominants are nearly identical... Good improvisers will liberally sprinkle their solos with both devices. A simple comparison of the notes generally used with the given chord [notation] and the notes used in tri-tone substitution or altered dominants will reveal a rather stunning contrast, and could cause the unknowledgeable analyzer to suspect errors. ... the distinction between the two [tri-tone substitution and altered dominant] is usually a moot point.<ref name="Coker 81">Coker, Jerry (1997). ''Elements of the Jazz Language for the Developing Improvisor'', p.81. {{ISBN|1-57623-875-X}}.</ref>}}

[[File:Tritone substitution and altered chord.png|thumb|right|Tritone substitution and altered dominant as "nearly identical"<ref name="Coker 81"/> {{audio|Tritone substitution and altered chord.mid|Play}}.]]

The alt chord is a heavily altered dominant seventh chord, built on the [[altered scale|alt scale]], a scale where every [[scale degree]] except the root is flattened compared to the [[major scale]]. For example, C<sup>7alt</sup> is built from the scale C, D{{music|flat}}, E{{music|flat}}, F{{music|flat}}, G{{music|flat}}, A{{music|flat}}, B{{music|flat}}. Enharmonically, this is almost the same as the scale for G{{music|flat}}<sup>7</sup>, which is the tritone substitute of C<sup>7</sup>: G{{music|flat}}, A{{music|flat}}, B{{music|flat}}, C{{music|flat}}, D{{music|flat}}, E{{music|flat}}, F{{music|flat}}. The only difference is C, which is the sharp eleventh of the G{{music|flat}}<sup>7</sup> chord. Thus, the alt chord is equivalent to the tritone substitution with a sharp–eleventh alteration.

The tritone substitution primarily implies a [[Lydian dominant scale]] or [[Lydian mode|Lydian]] [[Aeolian mode|minor scale]]. In the case of D{{music|flat}}<sup>7</sup> to C<sup>maj7</sup>, the implied scale behind D{{music|flat}}<sup>7</sup> would be D{{music|b}}, E{{music|b}}, F, G, A{{music|b}}, B{{music|b}}, C{{music|b}}/D{{music|b}}, E{{music|b}}, F, G, A{{music|b}}, B{{music|double flat}}, C{{music|b}}. Because of this, the extensions of 9, {{music|sharp}}11 and 13/{{music|flat}}13 are all available, while the {{music|sharp}}11 is where it shares with the altered scale.