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I have recently learnt about Augmented 6th chords. The examples in a music theory workbook had this chord written on the flattened submediant (6th degree of the scale). There was a small note in the book about this chord being written on the flattened supertonic (2nd degree of the scale) as well, but there were no examples.

How do you write an augmented 6th chord on the flattened supertonic, with examples? Is it different than writing the chord on the flattened submediant?

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  • I think the parallel 5th resolution of German Augmented 6ths belongs on a separate question. I'll just say that this resolution is common, though, to the point that my music theory textbook pointed it out.
    – Dekkadeci
    Jun 6, 2019 at 5:28
  • You mean I should separately ask that?
    – Grace
    Jun 6, 2019 at 5:29
  • Yes, and also remove that parallel 5ths question from this page.
    – Dekkadeci
    Jun 6, 2019 at 5:31
  • Alright, will do so.
    – Grace
    Jun 6, 2019 at 5:31
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    See also Neopolitan 6th chord.
    – John Wu
    Jun 7, 2019 at 5:54

3 Answers 3

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You write an augmented 6th chord on the flattened supertonic by applying the same Italian/French/German formula to the flattened supertonic as the conventional Italian/French/German Augmented 6ths do to the flattened submediant.

For example, in C Minor, the German Augmented 6th on the flattened supertonic is D♭ - F - A♭ - B, while the regular old German Augmented 6th on the flattened submediant is A♭ - C - E♭ - F♯.

For Italian Augmented 6ths, remove the 3rd note of each example chord. For French Augmented 6ths, move the 3rd note of each chord down a semitone (to G and D, respectively).

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  • I'm no expert, but are you sure the F♯ in your second example is correct? Shouldn't it be better written as G♭? Mixing sharps and flats seems strange to me.
    – MeanGreen
    Jun 6, 2019 at 5:37
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    @MeanGreen - Yes, I'm completely sure the F♯ in my second example is correct. The A♭- F♯ interval in the chord is why it is called an augmented 6th. Imagine writing more music in C minor, complete with secondary dominants, and you'll understand.
    – Dekkadeci
    Jun 6, 2019 at 5:48
  • That's mostly beyond my level of music theory, but is it because augmented means the note is raised by a half step, so F -> F♯? G♭ would probably suggest a lowered 7th, right?
    – MeanGreen
    Jun 6, 2019 at 6:11
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    @MeanGreen - Yes, A♭- G♭ suggests a minor 7th, while the "augmented" name for the A♭- F♯ interval is because that interval is 1 half step wider than a major sixth.
    – Dekkadeci
    Jun 6, 2019 at 6:15
  • A-F = minor 6th, A-F# = major 6th, Ab-F = major 6th, and Ab-F# augmented 6th (this is the definition of augmention of consonant intervals ...)
    – Albrecht Hügli
    Jun 6, 2019 at 12:25
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The most common version of this, in my experience, is actually the French augmented-sixth chord built on the lowered second scale degree.

In C, this creates D♭–F–G–B. This would be a French sixth in the key of F, but in the key of C it actually functions as an altered dominant. Since the V7 in C is G–B–D–F, this French chord on scale-degree ♭2 is just a V7♭5 in second inversion.

All voice-leading tendencies are the same. The difference, however, is in function. In F, this chord functions as a predominant leading to tonic. In C, however, this chord is a dominant that then leads to tonic.

Some people actually call this chord the FrV43 ("French V43") to show it's dual status a) as a French sixth and b) as an altered V43 chord.

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an answer to this question should at least contain the hint that this chord Db-F-Ab-B is used in Jazz as tritonus-substitution of the V7b5: G-B-Db-F-Ab (V7b5b9) the dominant 7 chord with dim5 and min9.

see example 2:

enter image description here

https://en.wikipedia.org/wiki/Tritone_substitution

and yes, the voice leading is the same as in the German 6th: we'll have the same 5th parallels as the "mozart fifths"

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  • Great reference to jazz! Although I have to admit, I've never ever heard a jazzist use the words "German 6th" instead of Tritone Substitution
    – Shevliaskovic
    Jun 6, 2019 at 10:25
  • @Shevliaskovic And they wouldn't. The Wikipedia article isn't saying that jazz people think of it that way, it's just pointing out that there's an equivalent outside of jazz. Jazz tritone substitutions aren't spelled as 6th chords, they're spelled as 7th chords. They're also called the "substitute dominant", it's the Dom7 chord whose root is a tritone away from the normal Dom7 of the given key. It's kind of a double tritone substitute: The substitute's root is a tritone away from the normal dominant, and, the whole reason it works is because those two chords both contain the same tritone.
    – Beanluc
    Jun 6, 2019 at 21:36

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