One of the most-often-used re-harmonization of the V7 is done by replacing that chord with the subV7.
Which chord is the subV7
The subV7 is a dominant chord a tritone away from the V7 (also a half step above the tonic or I)
Why does the subV7 work as a substitute of the V7?
There are two main reasons why this chord is such a perfect substitute for the V7
- The guide tones (3 & 7) are the same in both functions.
The 3 & 7 in the subV7 are the 7 & 3 in V7. The guide tones are the notes that give the chord its characteristic sound. In dominant chords, the guide tone (3,7) are a tritone apart. The tritone is an interval with lots of tension, [it used to be called “The devil’s interval” back in the middle ages] , which wants to resolve by moving each note half a step in opposite directions, thus turning into a major 3rd (when resolving inward) or a minor 6th (when resolving outward)
Example: In the key of C • G7 is the V7 • 3rd is B • 7th is F (since it is a flat seventh in dominants). B-F is a tritone. It wants to resolve either: inward to C-E (major 3rd) or, outward to Bb-Gb (minor 6th). A tritone apart from G is Db which would be the root of the subV7 in the key of C, and the guide tones in Db are F (the 3rd) and C flat (the flat 7th, which is B). Thus, we can resolve those two notes, as if we were in G7, to E and C, the tritone then resolves as expected in the key of C from Db7.
- The root of the subV7 is a half step above the I (tonic)
The bass-line for a V7-I progression moves down a perfect fifth (which is a very powerful bass movement).
When substituting the V7 with the subV7, the bass-line for the subV7-I is moving a half step down (which is as strong as the perfect fifth). Substituting the V7 with the subV7 gives us a strong bass-line that resolves tension well.
Here are the two examples using Mapping Tonal Harmony Pro 5 to view the different paths taken when using the V7 and/or the subV7 in the progression IIm7 – V7 – I (2-5-1)
In this introduction we will use mCircle to find the answer to a basic question (which could then be extrapolated into a more complex one)
Q. How many Major Triads are there in the Major Scale and in which degrees of the scale are they found?
The answer should be obvious to any beginner-intermediate theory student:
A. 3 major triads –> I, IV and V
Now let’s use mCircle to find the answer.
1. Launch mCircle. The layout has 4 main areas.
The Main Structure.
The sub-structure Candidate.
The sub-structures found contained in the main structure.
A list of the main-structure’s degrees where the sub-structures were found
2. In the main structure section choose Ionian from the popup labeled V1 by Name
3. In the sub-Structure Candidate section choose Major Triad from the popup labeled V2 by Name
And there’s your result: I, IV and V.
Now here’s a new question which I leave to the reader:
How many Minor Seventh Chords are there in a Dorian scale and where are they?
The “Decoding The Circle of Vths” Chart is laid out as a poster sized page of
18 x 24. In high resolution PDF format.
The chart is organized in six sections:
- The Circle and the Mode/Transposition Formula
- Symmetry and Inversions over the circle
- Limited-Mode Structures
- Most Common Source Scales and their Modes
- Secondary & Substitute Dominants
- Small Structures. Useful subsets candidates
Every structure is graphed over the circle of 5ths with its modal vector and the
M (# modes) number for that structure. All structure of limited mode are included in the chart. Major, Melodic and Harmonic minor and their modes. Small structures such as triads and tetrads are also included.
There are endless ways to apply the concepts presented in the “Decoding the Circle of Vths” chart. From jazz improvisation and voicings to tonal and atonal music composition and theory, many exercises and studies can be designed using this graphical approach to musical structures over the circle of fifths.
The eBook. Contents:
1. A formal intruduction to the concept and nomenclature. Definitions of modal structures, normal vectors, structure transformations and more, with examples and exercises for each one.
2. A description of the “Decoding the Circle Vths” chart’s layout and how to use it when applying the concept.
3. A set of exercises and ideas on how to apply the chart and concept to Jazz improv, Voicings, Composition and Arranging.
4. A brief manual on how to use the mCircle online software.
5. An appendix with worksheets for studying and applying the concept.
for more info visit mDecks.com