Section 21.2 Types of Augmented Sixth Chords
There are three general types of augmented sixth chords—the Italian augmented sixth chord (“ ”), the French augmented sixth chord (“ ”), and the German augmented sixth chord (“ ”). These geographic labels have persisted throughout the years despite the fact that no reasoning has been found for these designations. 1
All types of augmented sixth chords contain scale degrees ♭ and ♯ . To these two scale degrees, the adds . The three notes of the (♭ , ♯ , and ) form the foundation of the and . The adds to the Italian augmented sixth chord’s ♭ , ♯ , and , and the adds ♭ to the Italian’s ♭ , ♯ , and , as is shown in the example below.
The final chord on the first line—the Enharmonic German or —respells the ♭ as a ♯ because the resolves only to major . The does not occur in minor.
The 1964 Harvard Dictionary of Music states these chords are “rather pointlessly…distinguished as ‘Italian,’ ‘German,’ and ‘French’ sixth…”