The History and Classification of Augmented 6th Chords

Augmented sixth chords are a fascinating topic in music theory, particularly in the context of Western classical music. These chords serve a specific function in harmonic progressions and have a rich history that spans several centuries. This article explores the origins, history, and classification of augmented sixth chords, focusing on why they are distinguished as Italian, French, German, and Austrian variants.

Historical Background

Origins

The augmented sixth chord began to appear in the late 17th century, primarily in the works of composers during the late Baroque and early Classical periods. This period witnessed a significant evolution in harmonic language and the use of these chords became more prevalent in the following century. Renowned masters such as J.S. Bach and Haydn and Mozart were notable in their use of augmented sixth chords in their compositions.

Functionality

The chord plays a crucial role as a predominant chord, creating tension and resolving to the dominant V chord. The characteristic interval of an augmented sixth between the lowest note and the tonic helps to pull the harmony towards the dominant, adding a sense of unresolved yet compelling motion to the music.

Classification

Different types of augmented sixth chords are named based on their distinct intervals and the geographical associations with the composers and musical styles of their respective regions. Understanding these classifications provides insight into the rich tapestry of Western music and the theoretical backgrounds of composers.

Italian Augmented Sixth (It6)

The Italian Augmented Sixth (It6) is characterized by its simplicity and directness in harmonic function.

Notes

Typically consists of the root 6, the tonic 1, and the raised 4th 4. Example in C Major: C - F - A. Resolution: This chord resolves to G, the dominant.

French Augmented Sixth (Fr6)

The French Augmented Sixth (Fr6) is similar to the Italian variant but includes an additional note, the second degree, giving it a unique twist.

Notes

Similar to the Italian but includes the second degree. Example in C Major: C - D - F - A. Resolution: Also resolves to G, the dominant, but the added second degree adds a different flavor and voice leading.

German Augmented Sixth (Ger6)

The German Augmented Sixth (Ger6) is the most complex of the four and includes the root 6, the tonic 1, the perfect fifth 4, and the minor third 3.

Notes

Contains the root 6, the tonic 1, the perfect fifth 4, and the minor third 3. Example in C Major: C - E - F - A. Resolution: Often resolves to a dominant seventh chord G7 because of the presence of the minor third.

Austrian Augmented Sixth (Au6)

The Austrian Augmented Sixth (Au6) is a more complex harmonic variant often used in elaborate contexts.

Notes

Similar to the German augmented sixth but often used in a more complex harmonic context. Example in C Major: C - E - F - A and sometimes includes additional tensions or chromaticism. Resolution: It typically resolves in a similar manner to the German sixth but can lead to different harmonic progressions.

Conclusion

The classification into Italian, French, German, and Austrian reflects both the theoretical construction of the chords and their practical use in the music of different composers and styles. Each type of augmented sixth chord has a unique character and function within harmonic progressions, contributing to the rich tapestry of Western music. Understanding these chords is essential for both composition and analysis, particularly in the Romantic era and beyond where their usage became even more prominent.

By exploring the history and classification of augmented sixth chords, musicians and musicologists gain a deeper appreciation for the subtle nuances and rich harmonic language of Western classical music.