18a Discussion - Augmented sixth chords

AAAAAAAUUUUUGGGGHHHmented Sixth Chords

“What are they?”

• They are a collection tendency tones
• Their main purpose is to lead into a V chord
• They always contain an augmented sixth interval

“How are they made?”

• They all contain Do of their home key
• They all contain Le and Fi
• When spelled out, Le goes on the bottomm and Fi goes on the top. This is how you get an augmented sixth interval within the chord.

Italian:

• It⁺⁶
• Solfege: Le, Do, Fi
• Scale degrees: b6, 1, #4
• Italian is the “base model” version, which includes only the three necessary chord tones to make an augmented sixth chord.
• Le always resolves down to So, and Fi always resolves up to So. Do is the only chord tone that gets doubled, becuase it can resolve in different ways.

French:

• Fr⁺⁶
• Solfege: Le, Do, Re, Fi
• Scale degrees: b6, 1, 2, #4
• French adds “Re”, which can carry through to the V chord, not needing to move.
• Le always resolves down to So, and Fi always resolves up to So. Do will reslve to Ti if going to a V chord, and Re will remain as Re if going to a V chord.
• If it is used to go to a cadential 6/4 in minor, Re will go to Me.

German:

• Ger⁺⁶
• Solfege: Le, Do, Me, Fi
• Scale degrees: b6, 1, b3, #4
• German adds “Me”
• Le always resolves down to So, and Fi always resolves up to So. Me creates a voice leading issue because it resolves in parallel perfect fifths with Le. Because of this, German aug sixth chords often go to a I^6/4 and then to a V.

Additional Notes:

• The leadsheet notation for these chords are the same as the roman numerals.
• An augmented sixth chord is almost always predominant function, because they almost always resolve to V, or I6/4.
• There are no inversions of these chords, becuase they are not triads.
• Watch out for enharmonic re-spellings! In a real score, the accidentals on an aug sixth chord will be based on how each voice resolves, and may not match the accidentals you are used to seeing.

Steps for Building an Augmented sixth chord in any key:

1. Write in “Do”.
2. Figure out what is “So”.
3. Underneath Do, write in the note that is a half-step above So.
4. Above Do, write in the note that is a half-step below So.
5. If it is French, add in “Re” above Do.
6. If it is German, add in “Me” above Do.

Non-Standard Uses:

Ger⁺⁶ resolving to a I chord:

• In this case, the Ger⁺⁶ is acting with dominant function.
• It is labeled with a slash: Ger⁺⁶/ 1^{^}
• The slash and scale degree indicates what scale degree of the home key the augmented sixth interval resolves to.
• This is secretly a Tritone substitution (hip alert!)