MUS 212 Study Guide I (Chapter 9)

Augmented Sixth Chords:  Modulation and Other Uses

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  1. Since the sound of a German sixth chord is enharmonic with that of a major-minor seventh chord, its use as a pivot is effective and often dramatic.  The Gr6 chord may be respelled as any other Mm7 chord, or any Mm7 chord may be respelled as a Gr6.

  1. The Gr6 chord is commonly used as a pivot chord.  Three specific pivots account for most examples of this type of modulation.  They are:
  • V7 = Gr6 (modulation down one half-step),
  • V7/IV = Gr6 (modulation up a major third),
  • Gr6 = V7 (modulation up one half-step).

Each of the above pivots will reach four keys:  two parallel keys and the two keys enharmonic with these, if available (e.g., B, b; Cb, cb).  In each case, the spelling of the pivot is determined by the key of its destination.

Other Uses of the Pivot, Mm7 = Gr6

  1. The use of any other Mm7 chord in a Gr6 pivot is possible, though less common than those above.  One example is a modulation a fifth above, using the pivot V7/VI = Gr6.

Other Modulations Using the Gr6

  1. Occasionally, modulations will occur in which a Gr6 is involved, but not as a pivot.  See p. 271 for illustration of an example that modulates to the key of the mediant.

Spelling of the Gr6 Pivot

  1. Simply spelling enharmonically one note of the four-note chord changes a V7 to a Gr6, or a Gr6 to a V7.  For example, Ab, C, Eb, F# = Ab, C, Eb, Gb.
  1. When the new key has an enharmonic equivalent in the circle of keys, the pivot can be spelled enharmonically to reach that key.  (Spell enharmonically the lower three notes, retaining the same spelling for the upper note.)

Other Single Uses of Augmented Sixth Chords

  1. The above examples are the most commonly encountered. These chords, however, may also be used in other ways, including:
  • Inverted forms of the commonly used structures,
  • Chords so spelled as to resolve other than to the dominant tone,
  • Irregular resolution of the interval of the augmented sixth.

Augmented Minor Seventh Chords

  1. These are augmented triads with an additional interval of a minor seventh above the root.  Usually the #5 is the result of a chromatic passing tone.
  1. The interval between the chord's raised fifth and its seventh is a d3.  Although not an augmented sixth chord, the chord members are usually arranged so that the interval of the augmented 6th is displayed--the lower note of the interval usually found in an inner voice rather than in the lowest voice.
  • These chords, usually limited to the functions of V7 and V7/IV, are used infrequently. If desired, they can be labeled: V+7 and V+7/IV.

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