Harmony and Jazz Theory
Music scholars see jazz as a style of Western art music (read classical music; classical, however, is really the style of a certain period). All the harmony in jazz comes from that tradition, while the rhythms come from Africa. The vast majority of the jazz repertoire employs European harmonic forms and progressions. What is unique about jazz is the marriage of these European characteristics with African rhythm and a unique African-American style of inflections, articulations, and vibratos. The only set of tones used in jazz that is unique to Western art music is the blues scale (in C it would be: C, D#, F, F#, G, Bb, C), which is the result of the African-American fusion of slurs and glides (also a feature of African music) into the European major/minor tempered tonal system.
Since jazz has traditionally been characterized by the fusion of salient features of the two cultures, and the harmony comes from Europe, it is misleading to describe anything as jazz theory or jazz harmony. Even 12-bar blues is made up of a tonal progression of European chords (I, IV, and V, however, it can be dressed up in other European harmonies. Call it what you want, it’s still all European harmony.
Jazz texts simply codify what jazz composers choose to use stylistically from the full European palette, and sadly much has been left out, or rather not yet assimilated, like most 20th century music.
Therefore, it is better to go to the source, which is the classical harmony texts. French composer and theorist Jean-Philippe Rameau published the first definitive text on harmony in 1722. Books, by the way, will only prepare you for the real business of score analysis, which is where you’ll find the really relevant information: in practice, where it is most revealing.
As stated above, the blues scale is the only collection of tones exclusive to Western Art Music. While it is true, for example, that the minor seventh added to the root chord in a 12-bar blues constitutes a harmonic inclusion of a blues note, it nevertheless does not change the function of that chord in the progression, nor does it change the fact that it is a European progression. Although jazz is unique from European music due to its use of African rhythm, the rhythm does not alter the behavior of the progressions.
In the 20th century, many European composers began writing chord sequences that didn’t necessarily have a leading key (atonality), but this hasn’t caught on much in the jazz style yet. Unfortunately, jazz musicians and their audiences are stuck in old European harmonic forms and practices. In fact, most have not even fully digested the music of the French Impressionist composers Claude Debussy and Maurice Ravel.
It helps to understand a bit of music history to better understand the various styles that came into being. In a nutshell, it goes like this: In the West, music was modal until the late 16th century, at which point the music became tonal (based on chord progressions meant to culminate in a cadence to the tonic chord). The tonal system prevailed until the 20th century, when much music tended toward atonalism (no major key). In atonalism, chords are arranged in sequences that have no functionality in a tonal sense, but are used solely for their color and interest. Jazz, however, remains basically rooted in the harmonic practices of the classical and romantic periods (harmony of the 18th and 19th centuries).
Mark Levine’s popular book, Jazz Theory, is a good example of jazz educators’ limited understanding of music history. Basically, it executes the Berklee College system of applying chord scales and modes to chord progressions. This makes it necessary to theorize to arrive at which of these scales (arbitrary at best) should be applied. In this way, the Greek modal names apply to a tonal chord system that is by no means modal. In fact, 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 piece of history: A few years ago, while writing my Ph.D. thesis, I interviewed Jerry Coker, who was one of the first to hold a full-time position as a Jazz teacher at a college or university. . He admitted to me that he used this modal system, with its Greek names, to impress the classical administrators who dominated the music department, so that they would take jazz education seriously. (They have been in universities for over 100 years, whereas jazz education was only grudgingly admitted less than 50 years ago.)
Coker explained that if he had taught a more direct, common-sense, traditional approach to this extemporaneous art form, they would have missed it. They do not like us. The only reason jazz in higher education exists is because of enrollment: students demand jazz courses.