The Tritone, Substitution, Cycle 4
(22 Jan 04)
I had a computer printout from my old MacIntosh dated 1984, showing some cryptic chord forms I read once in a Tal Farlow interview. These were mostly altered chords which could be moved around in minor thirds and (more or less) belong to the same family of altered chords.
At one time I thought I understood this and filed it away. Due to recent discussion in the forum (eg. Cycles in General and Coltrane Changes), I was explaning something about tritone substitutions and moving tritones through cycle four, to a ex-student of mine and decided to get this out for reference.
It just so happened that I was thinking it was time to write a new article for Ibm.
So I got this (nearly) 20 year old sheet out and started trying to really understand it.
I got Excel up and started twiddling. I made a spreadsheet that allowed me to type in the intervals of a four note chord and show me the tensions of it and each copy of it moved up in minor thirds. This was a cool way to see what chords were usable as movable chord forms.(The Excel document is available for download in this forum thread)
I soon realized that it was going to take some time and effort.
To preface this I want to discuss the topic of Tritone movement through Cycle four and Tritone substitution.
All Dom7 chords contain a tritone between the third and the seventh (or vice versa since an inverted tritone is a tritone).
The jazz gurus tell us the third and seventh are the 'active' tones of the chord.
So these are the 'important' notes in a Dom7.
If you move from a Dom7 to it's tritone substitution you are basically pivoting on the tritone to a chord up a tritone.
Example: from A7 to Eb7 pivoting on C# and G which is the third and seventh of the A7 but becomes the seventh and third of the Eb7(actually Db is the seventh but it is enharmonic with C#).
So by pivoting I mean you keep the tritone note in place and move the root (and or fifth) to the new one. In this case I am talking about 3 note voicings.
Since a tritone is 6 half steps and a perfect fourth is 5 half steps, you can play the IV7 chord by moving the tritone down a half step (and the root up a perfect fourth).
So you can move tritones down chromatically to move through cycle four, just place the root accordingly.