More 8 tonic theory

In order to fully grasp the workings of the 8 tonic system we must first fully understand four tonic substitutions. Four tonic subs are also called diminished substitutions and the tri-tone substitution is included in this group of subs. If you can imagine that the tonic V7 and the tri-tone is one axis and that the V7 chords a minor third above and below is the other other axis (at a 90 degree angle from the first axis).

In the key of C the V7 is G7 and the tri-tone sub is C#7. The other two dominant chords are Bb7 and E7. These chords are all related to each other because they share the same diminished scale. A G7(b9), Bb7(b9), E7(b9) and C#7(b9) are basically all the same chord if you don’t consider their roots. The tri-tone is used all the time as the most common type of substitution, but the the other two dominant chords (Bb7 & E7) are also very common subs for V7. They are often used as ways to get to the tri-tone sub, this is called a ‘backdoor resolution’. 

For example:

D-7   G7    CMaj7

F-7 Ab-7  CMaj7

In fact, we can use the component chords of all four ii-7V7s and combine them freely.

B-7  E7    D-7 G7    F-7  Bb7    Ab-7  C#7

We can use only the dominants or only the ii-7s:

D-7       G7          CMaj7

G7 Bb7 E7 C#7   CMaj7

or play:
F-7       B-7         CMaj7

Keep in mind that the Dominant chords all sound pretty close to each other, the related ii-7s are where you start to get more dissonance. Think of the minor third axis  (B-7  E7, F-7  Bb7) as cousins of the tri-tone sub. The chords of the 8 tonic system are simply all of the chords from these these four ii-7V7s. When we are using hexatonics/pairs from these chords we are still basing the harmony these strong four tonic substitutions. The 8 tonic system is simply another way to apply hexatonics/triad pairs to diminished subs. We are just calling the related ii-7 chords Major triads (from the -3rd) or you can also think of them as IVs.


8 Tonics- All major keys play-along in Eb

8 Tonic System for Improvisation

The 8 tonic system is an attempt to organize and simplify the methods that have been used to teach improvisors to use Hexatonic/Triad-Pairs in the past. Hexatonic scales used for improvisation is now an important tool of the modern improvisor, yet there are inherent problems with the methods that have been taught up to this point. The biggest problem with Hexatonics is that they immediately sound formulaic and too much like a pattern. The other problem is that in order to use a wide variety of different Hexatonic/Triad-Pairs the player must commit many different formulas to memory in order to make the correct calculations to find the HT/TPs. These formulas are short calculations, like: Major triad from the #11 and Major Triad from the b13, but they start to add up and get overwhelming.

3 sets of 12 pairs
  Many players I have heard using triad pairs usually end up using the most basic pairs, like Major triad from root and Major triad from the 9 (which give a Lydian sound). Once you start opening up the options by considering all of the pair options of the modes of melodic minor then the world of Hexatonics will start to open up. Modes of Melodic minor are a perfect fit for the application of Hexatonics because there are no avoid notes any of the MM modes and every diatonic pairing sounds good. The 8 tonic system pretty much explodes the old system of applying Hexatonic structures to chord changes. We want to start seeing every ii-7V7 and every V7 that is resolving down a fifth in root motion as a set of 12 major triad pairs. These 12 pairs imply ii-7V7 cadences in four different keys, as well as different combinations of ii-7s and V7s drawn from two different keys.

The 8 tonic system can be considered as three different sets of 12 hexatonic triad pairings. Each set is functionally dominant, basically implying different combinations of ii-Vs in four keys. The result of applying these sets to normal ii-V7 progressions is that you set up symmetrical lines that are also highly chromatic. It feels very freeing to have eight possible major keys to choose from at any one time and this helps the improvisor to spontaneously create new ideas. By using half and whole-step hexatonics we are weaving different strands of the 8 tonic pretzel together.

 The justification for an eight tonic based system is this, the diminished scale should be the scale that our systematic improvisational harmonic model should be based on because the diminished scale creates all of the chords we use in Jazz. By combining two diminished seventh chords we are choosing exactly 2/3 of the 12 possible notes, which again gives us dominant function. The matrix below shows which chords come from a C diminished scale.