Jazz is a broad genre of music that takes the seventh chord as basic. (Traditional tonal music takes the triad as basic.) Jazz typically features mostly root-position extended or altered chords, syncopation, repetitive forms, and improvisation.

History and etymology

Jazz was invented in New Orleans at the turn of the twentieth century by African Americans: educated Creole musicians and migrant workers who brought the blues with them. They were forced to play together by Jim Crowe laws, which excluded blacks from concert halls. As popular music became more mass produced, jazz bifurcated, on the one hand evolving toward rock and funk and on the other hand migrating from popular venues to academia along with other historical styles. Today jazz encompasses New Orleans jazz, Kansas City jazz, Dixieland jazz, European jazz, Latin jazz, big band, bebop, free jazz, fusion, and other styles, and ironically it is more popular abroad than in the US.

The word jazz is related to the obsolete slang jasm for spirit or vigor. It is also related to the slang jism or jizz for spirit, spunk, or (coarsely) semen.

Harmony

Three kinds of chords (minor, dominant, and major), three harmonic idioms (II–V–I, I–VI–II–V, and I–II–III), and the process of tritone substitution are sufficient to understand the bulk of traditional jazz harmony. (For those keeping score, that’s three threes: 3 chords, 3 idioms, 3-whole-step substitution.)

Chords

There are tens of possible chords in jazz, but they can be summarized according to the possible members and tensions (extensions) of minor, dominant, and major chords: (i.e., the qualities of II, V, and I in major):

* The flat thirteenth of a minor chord would sound like the root of an inverted major chord.

** Avoid notes can also be used, but they should be treated as tones of figuration, e.g., passing tones, because they are considered dissonant.

*** Only for I in minor

Almost every chord in traditional jazz harmony can be classified as a minor, dominant, or major seventh chord. Half-diminished seventh chords can be considered minor chords with a flat fifth. Alternatively, both kinds of diminished-seventh chords can be considered dominant ninth chords with a missing root. Augmented-sixth chords are enharmonic dominants (see below), and augmented seventh chords are dominants with a sharp fifth. Lead sheets (scores with just melody and chord symbols) generally leave it to the player to determine what tensions to include. One can also “play outside the harmony,” i.e., play another chord over the given chord, creating a polychord. Such decisions depend on harmonic, voice-leading, motivic, and formal considerations, and a concern for variety.

Notice that the standard forms of minor, dominant, and major thirteenth chords tabulated above (m13, 13#11, and M13#11) can be rearranged into common scales:

Many jazz musicians consider the equivalence of chords and scales to be a fundamental principle of jazz harmony.

Idioms

The most important harmonic idiom in most jazz is II–V–I (or just II–V). A related idiom is I–VI–II–V (or its rotation VI–II–V–I). Both of these can occur in major or minor, using the same roots but different qualities (for I–VI–II–V, minor–minor–dominant–major versus minor b5–minor b5–dominant–minor).

Example: Henry Mancini, “The Days of Wine and Roses” (1962), arr. Art Farmer, mm. 9–16 (there should be a one-flat signature, scroll to 0:23)

F:    III (sub. for I)                   VI                                    II                                      V

d:     II                V             C: II               V                F: II                                      V

A second, less common idiom is I–II–III, sometimes featuring applied VII chords, i.e., I–VII–>II–VII–>III.

Example: Charlie Parker and Dizzy Gillespie, “Anthropology,” arr. Frank Paparelli, m. 1

Tritone substitution

Notice that changing just the root of three-voice dominant seventh chord to a note a tritone away (or, equivalently, transposing the entire pitch-class set by 6) produces another three-voice dominant seventh chord. The seventh becomes the third and vice versa:

Because of this close connection between dominant chords a tritone apart, one can substitute for the other. This process is called tritone substitution. In practice, though, tritone substitution is recognized not by the tritone (because the chord that is replaced is typically absent) but rather by descending half-step root movement instead of motion by fifth.

Example: Henry Mancini, “The Days of Wine and Roses” (1962), arr. Art Farmer: mm. 1–4. Eb7 (VII) substitutes for A7 a tritone away, because A7 (III) would serve as V of VI. Notice the half-step root movement Eb–D.

                        F: I                         VII (sub. for III)           VI

Tritone substitution happens in traditional tonal music, too: as shown below, augmented-sixth chords are enharmonically equivalent to tritone substitutes for V of V (that is why augmented-sixth chords can also be used enharmonically as V of bII, a tritone away from V). This enharmonic interpretation of augmented-sixth chords is shown here in parentheses:

Jazz simply extends tritone substitution from secondary dominants of V to all dominants. Notice how the augmented four-three chord has the same quality whether read enharmonically from the substitute root (VI) or from the written root (II). That is because the chord is transpositionally symmetrical, like a symmetrical scale.

Form

Jazz typically uses a repeated 12-bar blues form (most basically I––––, IV––I––, V–IV–I–– in major or I––––, IV––I––, VI–V–I–– in minor) or a repeated 32-bar song form, either AABA (a quatrain) or ABAC (a large period). The head or unadorned melody is typically played first and last, and additional repetitions provide opportunity for improvisation.

Example: Sonny Rollins, “Blue 7,” from Saxophone Colossus (1956): The bass and drums play two choruses before the saxophone plays the head.

Example: George Gerschwin, “I Got Rhythm” (1930): AABA, 32 bars with a 2-bar extension. The chord progression for this song is called rhythm changes.

Example: Henry Mancini, “The Days of Wine and Roses” (1962), arr. Art Farmer: ABAC.

Further reading

• Andy Jaffe, Jazz Harmony
• Mark Levine, The Jazz Theory Book

External links

Wikipedia has a brief article on jazz harmony with links to associated topics.