Tritone substitution in minor, just change the root or change the chord quality too?

Question

Recently I've been practicing rootless ii V i in minor jazz from Jerry Coker's Jazz Keyboard.

Here is the rootless chord chart...

Unless I missed something in the booklet, Coker doesn't specifically explain tritone substitution in minor.

I noticed that when the V chord root is changed to bII for the tritone substitution all the tones of V7#5#9 can be held and then the substitution becomes a plain V9 chord of bII9. So G7#5#9 becomes Db9.

Is that bII9 in minor a typical substitution in terms of chord quality? Or would some kind of altered dominant be more common? Certainly it sounds smooth to me, all the tones are held.

Also, would using a tritone substitution have any implications for the continuing i chord? I tried various combinations of imin6, imaj7, and imin7 and they all sound OK to me after a few repeats.

Answer 1

Usually the tritone substitution is played without alterations (apart from the #11), because the non-altered tensions (9, 13) are altered tensions of the original V chord: the 9 of the tritone sub is the b13 of V, and the 13 of the tritone sub is the #9 of the V chord. Of course, as usually, that's no rule but that's what is commonly done. You get an altered sound by playing the tritone sub, so altering the tritone sub would actually undo that effect.

As for the final i chord, I haven't noticed, neither in analyzing other people's playing nor in what I hear myself, that the choice of the tritone sub for the V chord implies anything concerning the exact realization of the tonic chord. Regardless of the choice of dominant chord, to me, the imin6 and the imaj7 (maybe with an added 9) sound more final than a imin7.

Answer 2

I don't want to speculate what is common or typical and what is not.

But what comes to the part of the question, is it any different in a minor key? I think the dominant and its tritone substitutions work just the same. It doesn't matter if it's a minor or major key - or at least that's how I like to play.

Then the question, "which alterations to the dominant vs the tritone substitute"... The alterations you do to the V chord affect what its tritone substitute becomes - assuming that you do the substitution by only moving the bass. However, there is a symmetric "equilibrium" where all notes except the bass stay the same. If you use such a symmetric chord quality for the V chord, then its tritone substitute will have the exact same chord quality. For example Bdim7/G: if you move the bass to Db, then the /Db chord has the same chord quality, because dim7 chords are have a symmetrical repeating pattern. If you move a note by any multiple of 3 semitones to either direction, it will have notes of the dim7 chord in the same relative positions.

If I understand correctly, how Barry Harris looks at things is, the "truest" jazz dominant is such that you can switch to its tritone substitute with all the same notes sounding. And so, you get the half-whole diminished scale starting from the V note. Or any of its alias names. (And which Barry Harris says must not be called "half-whole" because ... I forgot why)

The third part of the question - "should I be worried if I think it sounds good, but if it isn't common or typical" ... No? :) You're supposed to explore the sounds and use what you like.

Somewhat related to the question, if someone is interested in rootless chords, dominants and tritone substitutions, and what it sounds like, here's some rootless blues in C.

Try playing bass on that. Switch the bass between e.g. G and Db at will!