Augmented sixth chord

A German sixth chord on the last beat of m. 96 in Scott Joplin's "Binks' Waltz" (1905).^[1]

In music theory, an augmented sixth chord contains the interval of an augmented sixth, usually above its bass tone. This chord has its origins in the Renaissance,^[2] was further developed in the Baroque, and became a distinctive part of the musical style of the Classical and Romantic periods.^[3]

Conventionally used with a predominant function (resolving to the dominant), the three most common types of augmented sixth chords are usually called the Italian sixth, the French sixth, and the German sixth.