Nikolai Rimsky-Korsakov · section 86 of 96

The augmented sixth chord

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§ 82. — 1) To give a clear idea of the augmented sixth chords, we shall form them on the VIth degree of the harmonic major and minor modes, so that these altered chords, which derive from the IInd and the IVth degree of these two modes, will always have the VIth degree as their bass note.

Example (major, on A♭, the VIth degree of C harmonic major): a) chord derived from IV, A♭–C–C with F rising to F♯ (augmented sixth A♭–F♯), resolving either to t — Fig. 352 · See it in the reader

as well as:

Example (major): d) chord derived from II, A♭–C with D rising to D♯ and F rising to F♯ (♯6 ♯4 3), resolving to the C major 6/4 chord over G (6 4). — Fig. 353 · See it in the reader

Example in minor (C minor, three flats; A♭ is the VIth degree): a) chord derived from IV, A♭–C–C with F rising to F♯ (♯6), resolving either to the G major chord — Fig. 354 · See it in the reader

REMARK. — They can also resolve to the sixth chord of the IIIrd degree, in major as in minor.

a) Augmented sixth chord; enharmonic with the incomplete dominant seventh chord; it can occur in major and in minor.

b¹) Doubly augmented fifth-and-sixth chord; enharmonic with the dominant seventh chord with an augmented fifth; it can occur only in major.

b²) Augmented fifth-and-sixth chord; enharmonic with the complete dominant seventh chord; it can occur only in minor.

c) Augmented third-and-fourth chord; enharmonic with the dominant seventh chord with a diminished fifth; it can occur in major and in minor.

d) Doubly augmented third-and-fourth chord; enharmonic with the dominant seventh chord; it can occur only in major.

2) All the chords set out above, which, through the enharmonic equivalence of their augmented sixth, give the same sound as the dominant seventh chord, serve as a means of enharmonic modulation.

3) The names of these chords derive from the inversion of their fundamental chords.

4) The notes forming the augmented sixth must never be doubled.

5) Apart from their role as chromatic passing chords and as a means of modulation, they can also be used independently when they are prepared by the chord of resolution itself:

Example: each augmented sixth chord is preceded and followed by its own chord of resolution. (1) C major: G major chord; A♭–C–C–F♯ (♯6); G major chord. (2) C ma — Fig. 355 · See it in the reader

6) The augmented sixth has the following influence on the plagal cadences of the major mode, which we discussed in § 40:

Example: four plagal cadences in C major, each ending on the C major chord with C in the bass, the top part D rising to D♯ (the augmented sixth above the bass F — Fig. 356 · See it in the reader

REMARK. — Using augmented sixth chords and augmented fifth chords as independent, non-modulating sonorities is rather poor, because the effect of these chords in exercises is vague and bombastic; the student may nevertheless use them as passing chords.