Harmony and Jazz Theory
Music scholars view jazz as a style of Western Art Music (read classical music–classical, however, is really the style of a given a period). All jazz harmony comes from that tradition, while the rhythms come from Africa. The vast bulk of the jazz repertoire employs European harmonic progressions and forms. What is unique about jazz is the marriage of these European characteristics with African rhythm, and a unique Afro-American style of inflections, articulations and vibratos. The only pitch collection used in jazz that is unique to Western Art Music is the blues scale (on C it would be as follows: C, D#, F, F#, G, Bb, C), which is the result of African Americans fusing of slurs and sliding pitches (a characteristic also of African music) onto the tempered major/minor European tonal system.
Since jazz has traditionally been characterized by the fusion of the salient characteristics of the two cultures, and the harmony comes from Europe, it is therefore misleading to describe anything as jazz theory or jazz harmony. Even the 12 bar blues is comprised of a tonal European chord progression (I, IV, and V, however it may be dressed up with other European harmonies. Call it what you like, it’s still all European harmony.
Jazz texts merely codify what jazz composers stylistically choose to use from the entirety of the European pallet–and much has unfortunately been left out, or rather not yet assimilated, such as most of the music of the Twentieth century.
Therefore, you are better off going to the source, which is to classical harmony texts. French composer and theorist Jean-Philippe Rameau published the first definitive text on harmony in 1722. Books will only, by the way, prepare you for the real business of score analysis, which is where you will find the real pertinent information: in practice, where it is the most revealing.
As stated above, the blues scale is the only pitch collection unique to Western Art Music. While it is true, for example, that the added minor seventh to the tonic chord in a 12-bar blues constitutes a harmonic inclusion of a blue note, it nonetheless does not change the function of that chord in the progression, or change the fact that it is a European progression. While jazz is unique from European music due to its use of African rhythm, the rhythm does not alter how progressions behave.
In the Twentieth century, many European composers began to write chord successions that did not necessarily have a primary key (atonality), but this has not been incorporated into the jazz style very much as yet. Jazz musicians and their audiences are unfortunately mired in old European harmonic practices and forms. Indeed, most have not even fully digested the music of French Impressionist composers Claude Debussy and Maurice Ravel.
It is helpful to understand a little music history in order to better understand the various styles that emerged. In a nutshell, it goes like this: In the West, the music was modal until the late Sixteenth century, at which time the music became tonal (based on chord progressions aimed at culminating in a cadence to the tonic chord). The tonal system prevailed until the Twentieth century, when much of the music tended towards atonalism (no primary key). In atonalism, chords are arranged in successions that have no functionality in a tonal sense, but are used for their color and interest alone. Jazz, however, is basically still rooted in the harmonic practices of the classical and romantic periods (18th and 19th century harmony).
Mark Levine’s popular book, Jazz Theory, is a good illustration of jazz pedagogists’ very limited understanding of music history. It basically runs down the Berklee College system of applying chord scales and modes to chord progressions. This makes it necessary to theorize in order to arrive at which of these (arbitrary at best) scales are to be applied. In this way, Greek modal names are applied to a tonal chord system that is in no way modal. Indeed, the European composers, whom jazz musicians emulate, did not employ modes in tonal music: they used non-harmonic tones to propel their lines forward.
This is, I hope, an interesting tidbit of history: A few years ago, while writing my doctoral dissertation, I interviewed Jerry Coker, who was one of the very first to hold a full-time positon as Jazz Professor in a college or university. He admitted to me that he used this modal system–with its Greek names–to impress the classical administrators that dominated the music department–so that they might take jazz education seriously. (They have been in the colleges for well over 100 years, while jazz education was only begrudgedly admitted fewer than 50 years ago.)
Coker explained that had he taught a more direct, common sense traditional approach to this extemporaneous art form, it would have gone right over their heads. They don’t like us. The only reason jazz exists in higher education is because of enrollment: Students demand jazz courses.