19a Discussion - Augmented sixth chords

Class Discussion

Augmented Sixth Chords

The augmented sixth chord is not actually a triad. Instead, it is a collection of tones that resolve very smoothly in a specific way. These chords include the scale degrees Fi and Le (sharp fourth and sharp sixth scale degrees of the key you are currently in) which both resolve by half step to Sol. Because of this, they almost always resolve to a root position five chord. The interval between low Le and Fi above it is an augmented sixth.

These chords also all share another common tone: Do (the tonic). This tone often resolves down by step to Ti (seventh scale degree), becoming the third of the V chord. “Do” in an augmented sixth chord can also remain on Do and become the root of a I 6/4 chord.

Types of Augmented Sixth Chords

Italian Augmented Sixth Chords

In an Italian augmented sixth chord, the root of the key is always doubled. Therefore, there are only three unique notes in an italian augmented sixth chord: Le, Fi, and Do. These are also the only tones required for any type of augmented sixth chord.

French Augmented Sixth Chords

French augmented sixth chords include Le, Fi, and Do, but they also include Re, or the second scale degree. This tone often stays on Re to become the fifth of the V chord. If the french augmented sixth chord resolves to a I 6/4, the Re can resolve up to the third, or down to the root of the I 6/4 chord.

German Augmented Sixth Chords

German augmented sixth chords include Le, Fi, and Do, but they also include Me. German augmented sixth chords prefer to resolve to a I 6/4 chord. When they do this, Me often resolves up to the third of the I 6/4 chord.

The roman numeral notation is always either It+6, Fr+6, or Ger+6. There are no inversions to these chords, because they aren’t actually triads. The leadsheet notation for these chords are the same as the roman numerals.

The augmented sixth chord is almost always predominant, because they almost always resolve to V, or I6/4, both of which are always dominant.

Class discussion 2022

Augmented sixth chords

• Not based in tertian harmony, so their “Roman numerals” are written differently than normal
• They’re called augmented sixth chords because they contain an augmented sixth
• The primary reason for these is voice leading–the raised tone moves up, the lowered tone moves down. Both tones will proceed to the root of the next chord
  • a default +6 chord will proceed to V and has predominant function

Think of the components of these chords using scale degrees!

• Italian (It): b6, #4, 1 (x2)
• German (Ger): b6, #4, 1, b3
• French (Fr): b6, #4, 1, 2
• Ger+6 and Fr+6 are just It+6s with extra stuff!

Italian is the “basic” flavor: it just contains all the notes that all the +6 chords have. In my experience, I actually had more trouble IDing It+6 chords than the other two because I psyched myself out looking for a fourth tone that obviously was not there. So, be aware that It+6s are going ot have a different shape than Ger+6 and Fr+6.

Speaking of shape, Ger+6s will usually appear in the same shape as a V6/5, while Fr+6 will usually appear in the same shape as a V4/3. The default shape for a It+6 is like a V6. (V(7) is used as a filler for simplicity: remember that these all have predominant function.ex: Ab C Eb F# can be renamed as Ab C Eb Gb to make a Ab7 chord instead of Aug6 chord)

The “inversion” doesn’t affect how we label these. No matter which note is in the bass, it’s always written as the default (x)+6. This is because the chord is not made up of stacked thirds, so our inversion labeling system doesn’t translate properly.

Common fix for Ger+6 resolution: have it go to a I6/4! Also be aware that composers may enharmonically write any of the tones for voice leading purposes (again, the primary use of these chords is just cool-sounding voice leading)

Augmented sixth chords resolving to a non-dominant harmony

• By writing some notes enharmonically, we can basically sub in one dominant chord for another. In the example we did in class (in C), the respelled Ger+6 translated to a Db7, which still moved nicely over to V7.
  • Process: writing out the full chord (Db F Ab B) and respelling the B as a Cb. Cb wants to resolve down to the B in the next chord, and the F carries through to be the seventh.
• If you keep the chord as written, we have our normal +6 chord function: the actual +6 resolves outward to the root of the next chord. So our original +6 chord from the example resolves to a C major chord.
  • Labeling: instead of using our “in the key of” secondary dominant labeling, the slash indicates “going to” and you write the scale degree below the slash. The Ger+6 in this example would be written as Ger+6/^1 (remember the caret should be written above the number)
  • In this instance, Ger+6/^1 actually has dominant function, rather than predominant. It subs in for V7 and proceeds straight to I. Think of respelling the chord as a Db7! Ger+6s can have dominant function…but only sometimes

This was a lot of info, so here’s the most important things to remember:

• Tones of each kind of +6 chord
• How the different tones resolve
• Function(s) of a +6 chord