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I'm confused as to how to find these. For example, if I'm given a G-B-E# chord, how would I go about finding out what kind of chord it is, as well as what the tonic should be? I know the types of Augmented 6th chords, but not well enough to figure this out on my own.

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    For what purpose do you need this information? What things are affected if it "is a chord X" or if it "is a chord Y"? Is it for a theory exam? Dec 13, 2019 at 9:34

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In isolation, you have to rely on the spelling. And this might not be a terribly accurate guide as, even when the 'correct' spelling might be E♯, composers and copyists have a sneaky habit of writing F :-)

Not sure how you'd confuse an Augmented 6th with a Diminished 3rd? Maybe with a Minor 7th?

The good news is that we don't have to bother much with Augmented 6th chords these days. Not now that we've come to terms with ♭5 substitutions and the symmetrical ambiguity of the tritone (which is the same thing, really). In its typical pre-dominant position, the Italian and French varieties are best thought of as ii(♭5) or ii7(♭5), the German as the ♭5 substitute for ii7, ♭VI7. Functional names rather than mere labels.

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    "Not sure how you'd confuse an Augmented 6th with a Diminished 3rd?" - A dim3 is an inverted version of the aug6 interval. Some people occasionally refer to an inverted augmented 6th chord with #4 in the bass rather than b6 as a "diminished 3rd chord" rather than an augmented 6th, as the active interval is literally a diminished 3rd.
    – Athanasius
    Dec 12, 2019 at 22:41
  • @Athanasius - Yes, but a dim 3rd has a different name from an aug 6th. so confusion should not arise.
    – PeterJ
    Jan 1, 2020 at 12:17
  • @PeterJ: actually it often does not have a different name (see Michael Curtis's answer), since many sources still call these chords "augmented sixths" even when they literally don't contain an aug6 interval (instead a dim3). Anyhow, I'm not even sure if that was a confusion for the OP or if the confusion is in this answer assuming that OP was confused on that point. (i.e., I think OP may be simply asking something that could be better worded, "how can I easily tell if a chord is of class X, which also usually includes type Y?"). But OP has not clarified the source of any "confusion."
    – Athanasius
    Jan 1, 2020 at 13:14
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...I know the types of Augmented 6th chords ...if I'm given a G-B-E# ...what kind of chord it is

When you say types of augmented sixth chords, I think German, French, and Italian and that you are thinking of classical harmony. (This needs to be clarified, because augmented sixth chord look similar to tritone substitution chords in jazz. But, the two resolve differently.)

...what the tonic should be?

I think it may be a good idea to step through the augmented sixth interval first to see how it normally resolves which consequently will tell us the key we are in (the tonic.)

The augmented sixth is G up to E#. That is a dissonant interval and the standard way to resolve it is for the two tones to move in contrary motion by half steps expanding to an octave. G will half step down to F# and E# will half step up to F#. That F# will normally be the dominant of the key and the key will be minor. Go down a perfect fifth from that dominant of F# and we arrive at B so our key (the tonic) is B minor. Again, this is the standard resolution. It could resolve some other way, but we will skip that.

That standard resolution of the augmented sixth is the same for all augmented sixth chord types.

...Augmented 6th or Diminished 3rd?

That seems to be a question about how to identify augmented sixth chords when the tones are distributed into different octaves.

Let's notice that we could move the tones G and E# around with E# in the bass and the G in the treble - technically the interval would become a diminished tenth - but regardless of how the tones are distributed, if the chord resolves those two tones both to the dominant, we are dealing with an augmented sixth chord. In analysis it will be identified as an augmented sixth chord despite the fact the technical fact there may not be an actual augmented sixth!

Actually, this may explain why you asked about augmented sixth or diminished third. If the G and E# were placed so that they literally formed a diminished third but the resolution is like I described above, with the two tones moving to the dominant, we still call the chord an augmented sixth chord.

Sorry, to be so tedious, but the point I'm trying to get to is this: let's call G and E# the outer voices of the augmented sixth chord even if they literally aren't an augmented sixth apart. We sort of conceptually re-arrange what octave the tones are in. The reason to do this is because the inner tones will tell which type of augmented sixth chord it is.

One more tedious detail should be mentioned before examining the inner voices.

Let's imagine the chord in question is G B E using an E natural rather than E sharp. In B minor that chord is iv6 the minor subdominant in first inversion. A very common harmony progression is iv6 to V creating a half cadence. (That specific progression is sometimes called a Phrygian cadence.) In terms of voices B is the inner voice. This iv chord and the progression is the basis for two of the augmented sixth chord types.

If we take that progression, and raise the root of the iv chord - raise the E to E# in this example - we get the augmented sixth chord of your question! In terms of an altered root we have a kind of #iv chord. E# is the root, G is the third, and B is the fifth of the chord. The name of this particular chord is Italian augmented sixth chord. So an Italian augmented sixth chord is the augmented sixth G E# with an inner voice of B, an augmented sixth with a major third above the bass.

If we add another third on top of E# G B and make E# G B D, and then for analysis arrange it as G E# for the outer voices, then B D become the inner voices. Essentially we have taken our Italian augmented sixth chord and simply extended it to a seventh chord. It's the iv7 chord with the root raised. This one is called the German augmented sixth chord. A German augmented sixth chord is the augmented sixth G E# with inner voices B D, an augmented sixth with a major third and perfect fifth above the bass.

The final type of augmented sixth chord can be viewed as a variation of a different progression, but the outer voice/inner voice concern is still the same. Let's go back to starting with G and E as the outer voices with no chromatic changes yet. Let's add diatonic inner voices B C# so that we have G B C# E. That chord is C# half-diminished in second inversion, type of ii chord. If we raise the E to create our augmented sixth in the outer voices, it's an alteration of the third of the ii chord. This one is the French augmented sixth chord. A French augmented sixth chord is the augmented sixth G E# with inner voices B C#, an augmented sixth with a major third and augmented fourth above the bass.

What's an easy way...

Again, sorry for the tedious explanation above. It takes a lot of writing to get all the detail, but once your understand the origin of the chords, the mental process is pretty simple:

  • identify the augmented sixth as conceptual outer voices
  • classify the type by the inner voices (re-arrange the octave of the tones so they fit inside the augmented sixth)
    • major third above the bass = Italian augmented sixth chord (It+)
    • major third and perfect fifth above the bass = German augmented sixth chord (Gr+)
    • major third and augmented fourth above the bass = French augmented sixth chord (Fr+)
-3

The E# is rather odd and skews everything - diatonically, it immediately puts you into the key of F#, in which case B would be P4th and G would be m2nd - a very unusual sort of chord or chord fragment.

Consider the E# an F and you have a G7 chord without the 5th - G-B-F - a partial.

It's not unusual for a pianist or guitarist to drop the 5th for expediency's sake: The tonality and harmonic function of a chord is generally determined by its root, 3rd and 7th - G-B-F in this case. The 5th adds richness to the sonority of the chord but doesn't generally contribute to its harmonic function.

The 5th is optional particularly in ensemble playing where typically the bass or perhaps another instrument will be playing the 5th and fill out the sound.


Spelling and notation are often misleading or inconsistent, especially in modern jazz or rock contexts. In general, when you run into cases of unusual spelling - E# or B#, Fb or Cb being most commonly encountered - look at the other notes in the chord or lead sheet to guide you: do they make much sense in terms of the actual key indicated by the strange spelling? If so, go with it. If not, assume the odd spelling is not really correct given its context - consider E# to be F, B# to be C, etc.

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  • Changing E# to F results in a dominant seventh chord... not an augmented sixth chord. Dec 13, 2019 at 21:27
  • @MichaelCurtis - that's what I said - and therefore that chord should not be considered an augmented 6th. The OP asked how to figure out what chord that spelling might represent. - how would I go about finding out what kind of chord it is, as well as what the tonic should be? My answer is quite clear IMO - it's a partial G7 - 5th isn't mandatory in many contexts because the bass will play it.
    – Stinkfoot
    Dec 31, 2019 at 14:31
  • I think you are misunderstanding the question as an issue about a bad enharmonic spelling. The OP asked about augmented sixths and tonics. When you make your enharmonic "correction" of E# to F natural you change the context from an augmented sixth chord to a dominant seventh. You shouldn't do that, because the tonics will be different when you respell the chord. Your G7 will result in a tonic of C, or F# if G7 is a tritone substitution in jazz. When the chord is spelled with E# as the OP gave, it's an augmented sixth chord where the tonic will be B minor. Dec 31, 2019 at 16:15

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