Tri-tone substitution
The tri-tone substitution is an effective way to re-harmonize
a song without drastically changing the harmony and tonality. The basis of this topic will be PURE tri-tone intervals (6 semi-tones between the 3rd and dominant 7th note) and their use in dominant chord
harmony. The concept has a lot of versatility and I often use other quality of 7th chords (m7, M7) as substitutions,
even though they don't have a pure tri-tone interval. What matters most is
that the roots of the original chord and substitution are a tri-tone apart.
On the C6 tuning, I look for places where the tri-tone roots are close by on adjacent strings. For example, the tab shows a progression Dm7| G7 | Cmaj7, chords (1)(2)(3) in the tab. The G7 chord (2), with a root on fret 7, string 10, can be replaced by a C#7, chord (5), with a root a tri-tone away on fret 8, string 9, forming a Dm7 | C#7 | Cmaj7 progression, chords (4)(5)(6) in the tab.
Since the tri-tone interval is kept constant, this also works well in voice-leading. All we need to do is find a lead note and hold it constant.
So we can change the progression to Dm11 | C#7(#11) | Cmaj7, chords (7)(8)(9) in the tab, which now has a lead note of G. When playing this last progression, you might consider playing additional notes at the fret positions in order to realize the richer harmony of these extended and altered chords. For example, I will often play the C#7(#11) at fret 8 as shown in chord (10) of the tab. The same idea could be applied to the other chords as well.
1___________________________________________________________________________
2___________________________________________________________________________
3_____5___________________5___________________5(7___________7________________
4_________7R___7_______________8_____7______________8(7_____7________8(7____
5_____5___________________5___________________5______________________8(7)___
6_________7____7_______________8(6___7______________8(6_____7________8(6____
7____________________________________________________________________8______
8_____5___________________5___________________5______________________8______
9______________7_______________8_____7______________8_______7________8______
10________7_________________________________________________________________
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
Dm7 G7 Cmaj7 Dm7 C#7 Cmaj7 Dm11 C#7(#11) Cmaj7 C#7(#11)
Another place to do the tri-tone substitution for the Dm7 | G7 | Cmaj7 progression is shown in the
next tab, using chords (11)(12)(13). In this case I substitute the G root, chord (12), from fret 14, string 9, to the tri-tone C# root, chord (15) at fret 13 string 10, so that the progression now is Dm7| C #7 | Cmaj7, chords (14)(15)(16) in the tab.
1__________________________________________________________________________
2__________________________________________________________________________
3__________________________________________________________________________
4____14R____14_____12(7_________14R____13R___12(7__________________________
5__________________________________________________________________________
6____14(6___14(6___12___________14(6___13____12____________________________
7__________________________________________________________________________
8__________________________________________________________________________
9___________14______________________________________________________________
10___14____________12___________14_____13____12_____________________________
(11) (12) (13) (14) (15) (16)
Dm7 G7 Cmaj7 Dm7 C#7 Cmaj7
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