Glossary, Jazz Theory
There is no reason the well-established harmonic conventions in a century of jazz theory (or jazz harmony) cannot be divorced from the style of music where it was developed, jazz—with its swung beat and specific instruments, tempos, and moods—and used as a (partial) basis of generalizing harmony beyond the strictures of the common practice.
Indeed, jazz fusion, progressive rock, and progressive metal take this exact approach, even retaining some of the improvisational aspects of blues and jazz. (See also Tymoczko 2011 chapter 10 where the author highlights some of the direct influence of the early twentieth century scalar practice (Ravel, Debussy, Stravinsky) on jazz theory. Wynton Marsalis claims that “classical music is one of the foundations of jazz,” Sean Carroll’s Mindscape podcast, Episode 12.)
Jazz theory generalizes modes, allowing their notes to be played simultaneously, blurring the distinction between chord and scale (see Levine 1995), and allowing for shifting ensembles of jazz musicians to improvise together harmoniously (Tymockzo 2011, chapter 10). Groups of chords are collected into modes with the same root and the chords and mode are said to be compatible, so for example, the C Mixolydian mode is “played” vertically by voicing (or played over) either a C major triad, a C dominant seventh, or a C dominant ninth, etc. Avoid notes add some much-needed asymmetry and keep things from becoming too muddy and ambiguous.
For chromatic-cluster-free scales that span the octave and are made entirely of semitone and whole-tone (two-semitone) steps, there are only four possible scale types: the hexatonic (six-note) whole-tone scale, the heptatonic (seven-note) diatonic and acoustic scales, and the octatonic (eight-note) diminished scale. These scales, coupled with the chromatic scale, are the foundation of jazz theory and the focus of Harmonious. Other scales have varying degrees of importance harmonically.