Augmented 6ths

[Acciacatura]

I got curious today in a discussion about how the augmented 6ths (Italian, French, German) are formed. Can anyone explain it? At first it looked like it's based on the flattened 6 of the scale. In C that would be Ab-C-Eb with an F# but I have my doubts!

If anyone can clarify, thanks!

[ttw]

Originally Posted by Acciacatura

I got curious today in a discussion about how the augmented 6ths (Italian, French, German) are formed. Can anyone explain it? At first it looked like it's based on the flattened 6 of the scale. In C that would be Ab-C-Eb with an F# but I have my doubts!

If anyone can clarify, thanks!

That's it. The usual resolution is to have the Ab-F# interval expand to G-G. The inner voices can go to either B-D or Eb-C (followed by B-D) or E-C (followed by B-D.) The details depend on the desired voice leading.

[michael renardy]

Does the following chord have a name:

Ab - C - Db- F#

[MaestroX]

Does the following chord have a name:

Ab - C - Db- F#

I believe in the key of Eb major it would be the dominant b11th (5th ommited). I think that would be the best way to describe it

[Thorolf]

^ I’d call it a Db maj7 sus4 with Ab (the fifth) in the bass, interpreting the F# to Gb enharmonically.



Regards

[chckn8r]

Originally Posted by Acciacatura

I got curious today in a discussion about how the augmented 6ths (Italian, French, German) are formed. Can anyone explain it? At first it looked like it's based on the flattened 6 of the scale. In C that would be Ab-C-Eb with an F# but I have my doubts!

If anyone can clarify, thanks!

An augmented 6th is essentially a secondary dominant chord. It's along the same principles of using a bII7 to substitute for a V7. In the key of C, say you have a typical d7/f-G7-C progression, you can substitute the G7 with a Db7.

It works, because the G7 and the Db7 share the same tritone which in combination with the other notes gives the "desire" to resolve to the C chord. It's not as strong as the G7 because it doesn't have the falling fifth but it does have a cool sound. The problem lies in the fact that it introduces a lot of possible parallel voice leading because the fundamental, third and fifth are a semitone above the resolution points.

Now, in the augmented sixth case, you're essentially enharmonically spelling the Ab7 chord (Ab,C,Eb,Gb) which could be analyzed as a bII7 of V - substituting for the D7 chord which would be the V7 of V.

Hope it makes sense.

Dave

[reith]

Not so sure about that. Yes, the sound of the aug 6th is the same as the 7th on fixed pitch instruments but written/harmony, no.

Assuming the key is C:

the chord A-flat - C - D - F# (French)
or
A-flat - C - E-flat - F# (German)

definitely isn't a 7 because the interval A-flat to F# is an augmented 6th and the use is different. There's no reason why the chords shouldn't be used as pivots by way of enharmonic change but as they stand, they're 6ths. imho.

As I see it, these chords are derived from the second inversion of the incomplete chromatic supertonic (which is the same in major and minor). Still...I'm ready to be corrected.

[reith]

Originally Posted by MaestroX

I believe in the key of Eb major it would be the dominant b11th (5th ommited). I think that would be the best way to describe it

It's a nice chord. If the key is D-flat, it combines the subdominant and dominant.

(bass) A-flat - C (treble) B-flat - D-flat - G-flat.

[chckn8r]

Originally Posted by reith

Not so sure about that. Yes, the sound of the aug 6th is the same as the 7th on fixed pitch instruments but written/harmony, no.

Assuming the key is C:

the chord A-flat - C - D - F# (French)
or
A-flat - C - E-flat - F# (German)

definitely isn't a 7 because the interval A-flat to F# is an augmented 6th and the use is different. There's no reason why the chords shouldn't be used as pivots by way of enharmonic change but as they stand, they're 6ths. imho.

As I see it, these chords are derived from the second inversion of the incomplete chromatic supertonic (which is the same in major and minor). Still...I'm ready to be corrected.

It all depends upon the use and context of the chord. The way in which ttw was describing the resolution (to a G chord) suggests a secondary dominant use.

It also depends upon the sound, where you see the notes resolving and in which theoretical context you're analyzing the chord. In classical theory, your analysis is correct, but in jazz (or pop-music theory as some call it) theory, the German augmented 6th chord (followed by a dominant context) is usually viewed as an extension of a dominant progression - a chord borrowed from the parallel locrian scale.

The French version (Ab,C,D,F#(or Gb)) in jazz theory is viewed as the same, but analyzed as having a being an Ab7sus4 chord where the D may or may not resolve to the Eb before the next chord.

There are many ways to look at this, and it depends upon what context the chord is being used. Assuming the chord leads to an eventual dominant-tonic resolution, classical theory treats the chord as a special case or exception to the rule, whereas Jazz theory treats the chord as an extension of the dominant progression using modal interchange.

Just my two cents...

[stevel]

Originally Posted by michael renardy

Does the following chord have a name:

Ab - C - Db- F#

Most theorists just call this an "Augmented 6th chord" - the same for any that doesn't fit the Italian, French, or German versions.

FYI, Many people call "Swiss" the one that's an enharmonically spelled German:
Ab C D# F# instead of Ab C Eb F#

Steve