Music Theory for the 21st-Century Classroom

There are three general types of augmented sixth chords—the Italian augmented sixth chord (“${\text{It}}^{+6}$”), the French augmented sixth chord (“${\text{Fr}}^{+6}$”), and the German augmented sixth chord (“${\text{Ger}}^{+6}$”). 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 ♭$\hat{6}$ and ♯$\hat{4}$. To these two scale degrees, the ${\text{It}}^{+6}$ adds $\hat{1}$. The three notes of the ${\text{It}}^{+6}$ (♭$\hat{6}$, ♯$\hat{4}$, and $\hat{1}$) form the foundation of the ${\text{Fr}}^{+6}$ and ${\text{Ger}}^{+6}$. The ${\text{Fr}}^{+6}$ adds $\hat{2}$ to the Italian augmented sixth chord’s ♭$\hat{6}$, ♯$\hat{4}$, and $\hat{1}$, and the ${\text{Ger}}^{+6}$ adds ♭$\hat{3}$ to the Italian’s ♭$\hat{6}$, ♯$\hat{4}$, and $\hat{1}$, as is shown in the example below.

The final chord on the first line—the Enharmonic German ${}^{+6}$ or ${\text{EnGer}}^{+6}$—respells the ♭$\hat{3}$ as a ♯$\hat{2}$ because the ${\text{EnGer}}^{+6}$ resolves only to major ${\text{I}}_4^6$. The ${\text{EnGer}}^{+6}$ does not occur in minor.