The term "Hexatonic Triad Pairs" is actually a redundant phrase, or something known as a "pleonasm". It is, however, accurately self-descriptive and rolls off the tongue quite easily.
A true triad pair - which is formed from 2 adjacent triads and therefore comprised of 6 non repeating notes - always results in a hexatonic (6 note) scale. On the other hand, a hexatonic scale, being any scale of 6 notes, doesn't always yield a triad pair.
The four Major Scale triad pair formations examined here are:
- I & ii or V & vi (1 Maj & 1 min triad a whole step apart - eg. C Maj & D min of C Maj or F Maj)
- ii & iii (2 min triads a whole step apart - - eg. D min & E min of C Maj)
- iii & IV (1 min & 1 Maj triad a half step apart - eg. E min & F Maj of C Maj)
- IV & V (2 Maj triads a whole step apart - - eg. F Maj & G Maj of C Maj)
So, what happened to vii & I (B dim & C Maj), you say? Well my best explanation is that in order to keep the size of this volume manageable at 217 pages, I thought it best to relegate this triad pair to a future volume. Fair enough?
Since all the above pairs are derived from Major Scale harmony, the sonic and qualitative differences can be either subtle or more pronounced, depending on and according to their context.
All exercises and sequences shown as examples are presented for each triad pair in all keys.
The first pair of triads, C Maj & D min (C-E-G & D-F-A) is derived either from scale steps I & ii of C Maj, or V & vi of F Maj.
In either case, this is illustrated in Ex. 1 below with both triads stacked together in a continuous, ascending direction:
Ex 1.
Ex 2.
With D as the root, both the triad pair and hexatonic have a pronounced min7 11 color.
The strongest modal "pull" of this hexatonic besides Major (Ionian) is probably Dorian or Aeolian. Since it's derived from either C or F Maj, both B and /or Bb are implied as the 6th degree of the aforementioned minor modes, respectively.
Ex 3.
Ex 4.
Modally, this hexatonic has a decided Phrygian or Lydian flavor, and due to the presence of a tritone (A – Eb), it has a strong pull, harmonically, to its home key of Bb.
In many discussions of triad pairs that I've seen or read about, this configuration seems to be “the triad pair”, as if it were the only one in existence.
In its defense, however, it is probably the most versatile of the bunch, being heard as early as 1959 as part of John Coltrane's solo on Miles Davis' video version of “So What”, as well as several years later on 'Trane's own quartet version of his composition “Big Nick”.
It had already been featured long before that as part of the Afro -Cuban son.
Ex. 5 shows an ascending sequence, alternating between G Maj & A Maj triads (IV & V of D Maj). F#, the 3rd of D Maj, is in this case, the omitted tone.
Ex 5.
Ex 6.
You can hear an example of this is in bar #4 of Ex. 9 below (C Maj7 #11).
In the following 4-bar ii-V7 examples, the main chord symbols are on top of the staff, as is usual, while the letter names of the individual triads (one pair per measure) are listed under the staff beneath each triad's contiguous note grouping.
Ex 7.
The breakdown for this one is pretty simple:
Bars #1 & #2 each use a IV & V triad pair (from Eb & Gb Maj, respectively); while bars #3 & #4 utilize a ii & iii pair - (from Bb Maj).
The pairs are: in bar #1 - IV & iii, bar #2 - ii & I, bar #3 - ii & I, bar #4 - IV & V
The main objective, once comfortable, is to turn these lines into real music.
Exercises and sequences should be practiced in all directions, using rhythmic diversity (rests, triplets, etc.). Concepts, inversions and permutations from “Triadicisms, Vols. I & II” could be incorporated here with great effectiveness.
With a little passion, patience and practice, you will no doubt, sooner than later, reap the sweet fruits of your labor.
So, take a bite out these "pairs"!
B. Stern