Forum: music.stackexchange.com
Tags: <harmony><modulation>
Title: Can I use the German sixth chord to modulate to another key?
Question: Can I use the German sixth chord to modulate up a half step?  For example, the Ger6/5 chord in C major is: Ab-C-Eb-F#, which is enharmonically equivalent to G#-B#-D#-F#, i.e. the dominant chord of C# major.

Answers:
sents: text: All of these answers are correct, but I thought it would be helpful to the OP (and hopefully future readers) to give some clear examples.
text: The above example is just a clear use of a German augmented sixth in C minor.
text: The Ger+6 is on beat three of the first measure, and it proceeds to a V on beat 4 and then to tonic in the next measure.
text: (For the sake of simplicity I'm ignoring the parallel perfect fifths between beats 3 and 4.)
text: Hear this example.
text: This example shows how one can use the Ger+6 to modulate up a half step.
text: (We can also say it "modulates to the Neapolitan," because the Neapolitan is the lowered second scale degree, which is just a half step above tonic.)
text: Notice that beat 3 of this first measure is the exact same chord as it was in the first example.
text: On beat 3 here, we have another Ger+6 in C minor.
text: But on beat 4, I respell the F♯ to show that it is enharmonic to G♭.
text: Because of this, beat 4 is suddenly a V7 in the key of D♭, which is where it resolves in the next measure.
text: The key point here is that a Ger+6 sounds just like a V7, but they aren't spelled the same.
text: Hear this example.
text: To take this one step further, this example is now in D♭.
text: It's just a basic D♭ progression with a V7 on beat 3 of the first measure.
text: (You'll notice that beat 3 is exactly the same in each of these examples.)
text: Hear this example.
text: We've shown that the Ger+6 and a V7 sound the same, and we've used that to turn a Ger+6 into a V7 of another key.
text: But why not turn a V7 into a Ger+6 of another key?
text: That's what I show in this example.
text: On beat 3 of the first measure, I write a V7 in D♭.
text: But notice that I use F♯ and not G♭, because now I'm using the V7 in D♭ as a Ger+6 in C. Beat 4
text: is then a V7 in C, and I return to C in the final measure.
text: Hear this example.
text: Lastly, you may also be interested in checking out "Punning chord"
answer_details: author: music.stackexchange.com/users/21766/Richard
score: 8
sents: text: Hippie answer:
text: You can do whatever you want.
text: Constructive answer:
text: Yes, this is a good way to modulate up a half step.
answer_details: author: music.stackexchange.com/users/10290/MattPutnam
score: 7
sents: text: Yes, the German Augmented 6th in C is a re-spelt Ab7, which will naturally lead to Db.
text: Some might say a little TOO naturally - but then, 'up a semitone' is the ultimate cliché modulation, so why not revel in it!
answer_details: author: music.stackexchange.com/users/17003/Laurence Payne
score: 3
sents: text: A German Augmented 6th sounds like a dominant, but the entire reason for the goofy spelling is to change the function / voice-leading of the chord.
text: Gr+6 typically function as pre-dominants, so as long as you make it a pre-dominant for your secondary-dominant or secondary leading-tone chord, then you’re good to go for modulations.
answer_details: author: music.stackexchange.com/users/3518/jjmusicnotes
score: 1
sents: text: Whether one of these chords is a "pre-dominant" or "dominant" depends on usage.
text: If the tones comprising the outer interval (the augmented sixth or dominant seventh enharmonic) each move outward by a half-step, the chord is being resolved as a dominant sixth.
text: For example, the chord Ab-C-Eb-F# resolves to G-C-E-G and then to G-B-D-G (or G-B-D-F), the first chord is acting as an augmented sixth.
text: The German Sixth acts a pre-dominant moving to the dominant through another pre-dominant the C64.
text: If the chord is notated (or could be thought of as being notated) as Ab-C-Eb-Gb and the Ab moves to Db with the Gb dropping down to F, and other intervals moving to notes of the Db chord (being careful to avoid parallel, etc.)
text: the German Sixth is behaving (and is notated) as an ordinary dominant.
text: In both cases, the tritone resolves correctly as either an augmented fourth or a diminished fifth (outwardly and inwardly respectively.)
text: Enharmonically speaking, the German Sixth is the dominant of the Neapolitan Sixth.
text: While the above operations are not symmetric, they are reversible.
text: With proper voice leading into the German Sixth (or dominant seventh), either is useful.
text: The main difference in the interpretations is that in the German Sixth, the lowest and highest notes each expand by a half step; in the dominant seventh, the highest note moves up and the lowest note moves up a fourth or down a fifth.
text: Chopin's Op 40 Polonaise # enters as a German Sixth and exits as an dominant seventh.
text: Some other examples (also using the idea of tritone substitution) are given here: http://www.mtosmt.org/issues/mto.08.14.2/mto.08.14.2.biamonte.html
answer_details: author: music.stackexchange.com/users/23838/ttw
score: 1

Summary of the answers:
A German Augmented 6th sounds like a dominant, but the entire reason for the goofy spelling is to change the function / voice-leading of the chord.   Gr+6 typically function as pre-dominants, so as long as you make it a pre-dominant for your secondary-dominant or secondary leading-tone chord, then you’re good to go for modulations.
A German Augmented 6th sounds like a dominant, but the entire reason for the goofy spelling is to change the function / voice-leading of the chord