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Old 12-15-2017, 10:45 AM   #1
zanshin777
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Default Tritone Substitution

https://youtu.be/r0XKX5Cy2vQ?t=1333 (Pinpointed Link)

He says these chords are the same chords with different root. But they are not.

Db7b5 : Db-F-G-B

G7#5#9 : G-B-D#-F-A#

??
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Old 12-15-2017, 02:39 PM   #2
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I can't watch the vid at this time, so there may be some details in his explanation that I'm missing. But the general theory of the tritone sub goes like this:


Simplify things to G7 and Db7:

G7 = G B D F

Db7 = Db F A Cb (B)

The tritone interval is the same in both chords; B to F and F to Cb (B). The tritone interval is what makes a Dominant 7 chord function so well. So Jazz guys figured out that these two chords can be subbed for each other and you get the same function.


With the chords in your example you're dealing with what jazz guys call Altered Dominant chords... b5/#5 and b9/#9. For the most part once you get to altered chords, one is as good as the next. In fact on a lot of jazz charts you'll just see G7alt... any alterations will do.

So G B D# F A# = G7alt (G7#5#9) and G B Db F = G7alt (G7b5)

They are functionally the same chord.

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Old 12-17-2017, 06:52 PM   #3
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Quote:
Originally Posted by zanshin777 View Post
https://youtu.be/r0XKX5Cy2vQ?t=1333 (Pinpointed Link)

He says these chords are the same chords with different root. But they are not.

Db7b5 : Db-F-G-B

G7#5#9 : G-B-D#-F-A#

??
I've said this before, but you really need to stop watching these Rick Beato videos! He does know his stuff but he's not great at explaining it. and I'm not surprised you keep getting confused.

Anyway...

The chords they begin from are identical.

Db7b5 = Db F G Cb(=B)

G7b5 = G F Db B

What happens then is that other notes are added. If we're starting from G7 (because the key is C), we're altering the 9th as well, and also allowing the raised 5th as well as the flat 5.

So we end up with (possibly) G7#5#9= G B D# F A#.
We could also have G7b5b9 = G B Db F Ab.

We could also have G7#5b9, or G7b5#9.

The tritone sub (Db7) adds extensions from the same series of notes.
So Db7 could keep its perfect 5th (Ab). And we could add the 9th (Eb=D#), the #11 (G), or the 13th (Bb=A#). So we could have Db13#11 (in full):

Db-F-Ab-Cb-Eb-G-Bb - although in practice we probably wouldn't use the whole scale!

The crucial thing about the tritone sub is it must retain the original 3rd and 7th - the inner tritone in the chord. That's B-F in this case. We can put a G or Db bass on that:

G-B-F = G7 (no 5)
Db-F-Cb = Db7 (no 5)

Either of those chords could resolve to either C or Gb. But now the issue is if we pick C as the target chord, that governs the other chord tones we choose.

G7 - we add b5, #5, b9 or #9
Db7 - we add 5, 9, #11 or 13

This is all the same 7 notes, remember - known as either the "G altered" scale, or the "Db lydian dominant" scale. (Some people like to think of it as "Ab melodic minor", but IMO that's not very helpful.)

The reason for the scale is how all these notes all resolve to chord tones (or extensions) on the C chord. Here's how every note of the scale resolves to any note of a C6/9 chord (C E G A D):

G = shared tone
Ab > G or A
A#/Bb > A
B > C
Db > C or D
D#/Eb > D or E
F > E

You can see that everything aside from G moves by half-step up or down. This is the whole reason for altering a G7 chord (or using the tritone sub) in the first place: to maximise the options for chromatic voice-leading.

If we were using G7 or Db7 to resolve to Gb major - i.e., if G7 was tritone sub for Db7 - then we'd using different alterations.
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Old 12-20-2017, 06:40 PM   #4
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What can we use rather than those chords I wrote below in the context of "tritone substitution"?

I know the ingredients of those. However I couldn't express them because of the tricky chord notation.

1) G7#5#9 : G-B-D#-F-A#

2) G7b5b9 : G-B-Db-F-Ab

3) G7#5b9 : G-B-D#-F-Ab

4) G7b5#9 : G-B-Db-F-A#
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Old 12-21-2017, 12:45 PM   #5
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Quote:
Originally Posted by zanshin777 View Post
What can we use rather than those chords I wrote below in the context of "tritone substitution"?

I know the ingredients of those. However I couldn't express them because of the tricky chord notation.

1) G7#5#9 : G-B-D#-F-A#

2) G7b5b9 : G-B-Db-F-Ab

3) G7#5b9 : G-B-D#-F-Ab

4) G7b5#9 : G-B-Db-F-A#
The tritone sub for all those chords is a Db7, with optional 9, #11 and/or 13 extensions. Ie., Db-F-Ab-Cb, to which you can add Eb, G and/or Bb.

IOW, in chord-scale terms, the tritone sub for a G altered chord is a Db lydian dominant chord. Mainly because it shares the crucial inner tritone (B-F), but because the other notes all come from the same scale (as you can probably see ).

All of them are designed to resolve to Cm or C major.

The reason for choosing which extensions you add to the Db7 is the same as the reason for choosing which of those altered G7s to use: whichever offers the voice-leading you want between the chords either side.
IOW, all those G7alt chords are equivalent in function - which is why you see "G7alt" in some chord charts, leaving the choice (the permutation of 5 and 9) to you.
Usually, for a tritone sub, you'd probably keep any specified alterations. Eg, for a G7#5#9, you'd probably want a Db13(#11), including the 9th. For a G7b5b9, Db7#11 is enough. But really that's just about keeping the main part of the chord and just changing the bass note from G to Db.

Playing the various options, in context, should reveal how it all works.

Last edited by JonR; 12-21-2017 at 12:54 PM.
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Old 12-26-2017, 06:05 PM   #6
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1)

Quote:
Originally Posted by JonR View Post
The crucial thing about the tritone sub is it must retain the original 3rd and 7th - the inner tritone in the chord. That's B-F in this case.
Why 3rd and 7th rather than 1st or/and 5th?

I thought it's tritone substitution because of G to Db is 3 whole step aka tritone.


2) How do we apply tritone substitution I mean in the chord sequence at first take we use original chord (G7) and the repeat of the sequence we use tritone substitution chord in the relevant place. Like that?
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Old 12-27-2017, 12:58 PM   #7
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Quote:
Originally Posted by zanshin777 View Post
1)


Why 3rd and 7th rather than 1st or/and 5th?
Because the 3rd and 7th is the dissonance that drives the chord function.

If you move the roots of other chord types by a b5, they don't work the same way. Eg, Dbmaj7 is not a sub for Gmaj7. Dbm7 is not a sub for Gm7.

If you just use the plain triad - Db in place of G (going to C or Cm) - it does work, but not quite as well, because you miss the leading tone. The shared tritone (with dom7s a tritone apart) is crucial for the chords to function in the same way.
Quote:
Originally Posted by zanshin777 View Post
2) How do we apply tritone substitution I mean in the chord sequence at first take we use original chord (G7) and the repeat of the sequence we use tritone substitution chord in the relevant place. Like that?
Yes. Or you can just use Db7 instead of G7 any time; you don't have to have heard the G7-C first.

Bear in mind it has to suit the song. Tritone subs have an obviously jazzy-bluesy effect, which doesn't suit everything. And you need to watch out for the melody too. So if the melody holds a D over the G7 chord, then you can't replace it with Db7. (Technically you could use Db7b9 in that case, but it's a rare choice - sounds too dissonant for most ears.)

Also, the G7 has to be a V7, i.e., going to either C or Cm. Not every G7 will be doing that.
Of course, if the G7 is resolving down to F# or F#m, then it's already a tritone sub, and you could revert to the standard V chord, C#7!
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Old 01-02-2018, 10:51 AM   #8
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Thank you very much JonR for your detailed answer.
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