I'm trying to understand an interesting non-diatonic chord in the chord progression at 0:30-0:45 of this video; my rough transcription of the chords is as follows. enter image description here

  • As far as I can tell, the non-diatonic chord is a tritone substitution for C#7 (the dominant of the following chord F#m) or C#m7 (the vi in E). Is this a fair assessment of the chord's function?
  • Is my naming of G9add13 correct? I don't think it's a G6/9 because of the presence of the F. More generally, is there a broader name for this particular kind of voicing, like "quartal upper structure"?

Thank you again.

  • There is a minor triad, E G B, in there. The F natural would be a b9 and the A an 11. But that view doesn’t simplify anything. Mar 4, 2021 at 4:04

2 Answers 2


Your assessment is right, so is the voicing you wrote. It is a G13 chord (7,9,13) and it is a substitute dominant chord for C#7 going to F#m7. The strong G root, presence of the B and F notes in the chord and the function to the F#m leaves no doubt in my mind that it is a G dominant chord and not a slash or inversion chord.

I think quartal voicing is pretty accurate (two 4ths, one tritone). It is also a drop 2 voicing of (bottom to top) B-E-F-A or 3,13,b7,9 (with the low root added) which is a typical way players with a jazz sensibility voice dominant chords without altered tensions in one hand. FYI this same voicing can be used for a C#7alt chord by changing only the root from G to C#.


Yes, it's a substitution, but it's not G9add13, it's A7/G, or better, A7sus2/G.

  • How is it A7 with no C# and an added F? OP is correct, it's a G9add13, and it's a tritone substitution for C#7 in a ii-V-i progression.
    – Aaron
    Mar 4, 2021 at 3:17
  • Ahh, I see. Sus2. Still, makes no sense: doesn't explain the F and doesn't fit functionally.
    – Aaron
    Mar 4, 2021 at 3:19
  • @Aaron well, using suspended/quartal chords the concept functionality becomes more "volatile" than the "standard" approach that is based on abstractions. G9add13 is not that different from A7sus2/G, and the most important notes of the substitution (the bass, and, considering the following chord, the third) do exist. It lacks the seventh, yes, but it doesn't matter that much. Mar 4, 2021 at 3:42
  • No offense, but the G13 analysis makes a lot more sense in context. Try reducing the chords down to seventh chords, and G#m7 G7 F#m7 still has clear function in E major. G#m7 A7 F#m7 is a lot less functional. Also, the correct chord name for your A-rooted analysis would be something like A9b13(no3) in third inversion, which is uncommon harmony compared to the logical tritone substitution G13. It's not wrong objectively, but it's also not a very useful understanding of what's going on here.
    – user45266
    Mar 9, 2021 at 21:58

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