When working through some of Barry Harris’ ideas on chord/scale relationships it occurred to me that the eight-tone or octatonic scales found in his method can be generated by taking the chord tones of the chord you wish to imply and fill with the notes of the diminished seventh chord that is built one half-step below. For example:
GMaj6 chord tones are G-B-D-E.
The diminished seventh chord one half-step below is F#dim7: F#-A-C-Eb.
Combining these two chords to form a scale gives us:
G-A-B-C-D-Eb-E-F#-G.
In jazz this scale is often referred to as “bebop major” which is generated by the insertion of a chromatic passing-tone (in this case between fifth and sixth scale degrees) in a major scale in order to prominently place the chord tones on strong beats. In my examples I have the chord tones shown as open note heads and the passing tones as filled note heads.
This related diminished seventh chord is known as a “leading-tone diminished seventh chord” since its function is to “lead” into or resolve to another harmony one half-step above as vii in major and #vii in minor (harmonic minor) resolve to tonic (i).
The idea is to take each of the four remaining common chord types (Major6, Dominant7, minor7 and minor6) and build an octatonic scale with the above system. Remember the minor6 chord is equivalent to the m7b5 or half-diminished seventh chord spelled from the sixth.
We end up with three of the most common bebop scales (bebop major, bebop natural minor and bebop melodic minor) as well as one unique scale for the dominant seventh chord that I refer to as the fifth mode of melodic minor with chromatic passing-tone. It is almost the same scale as the bebop dominant with the exception of the lowered sixth scale degree. I am still not sure about this one. My ear wants to hear the major sixth as in the bebop dominant scale.
Harmonizing these scales using only the fundamental seventh or sixth chord and the passing diminished seventh chords gives us a very useful way of filling space in charts that have rather static harmony as well as a way of learning the inversions of the basic chord types.
Try using these new octatonic scales when improvising over their corresponding chord types. You may find some fresh sounds and some familiar sounds heard in the solos of the great players of jazz.