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Augmented sixth chords are a fascinating aspect of Western music harmony, often used to create tension and resolution in compositions. Among the various types, the Italian, German, and French augmented sixth chords are the most prominent. Understanding their differences helps musicians and students grasp how composers evoke emotion and structure in their music.
Overview of Augmented Sixth Chords
Augmented sixth chords are built on intervals that span an augmented sixth, typically between two notes a diminished third apart. These chords usually include a characteristic augmented sixth interval, which resolves outward to a perfect octave, creating a sense of tension and release. The specific notes and their resolutions define the type of augmented sixth chord.
The Italian Augmented Sixth (It+6)
The Italian augmented sixth chord, also called It+6, is built on the notes of the tonic, the lowered sixth, and the raised fourth scale degree. It typically includes the root, the lowered sixth (♭6), and the augmented sixth interval, which is enharmonically equivalent to a major seventh. The chord often contains the note ♯4 or ♯11.
In its most common form, the Italian augmented sixth chord consists of the notes:
- Root (often the tonic or a related pitch)
- ♭6 (lowered sixth)
- ♯4 (raised fourth)
This chord resolves outward to the dominant, with the augmented sixth interval closing to form a perfect octave.
The German Augmented Sixth (Ger+6)
The German augmented sixth, known as Ger+6, differs by including an additional note, the ♭3, which gives it a richer harmonic color. It is often spelled with the notes:
- Root (typically the tonic or related pitch)
- ♭3 (lowered third)
- ♭6 (lowered sixth)
- ♯4 (raised fourth)
The presence of the ♭3 makes the German augmented sixth more complex, and it typically resolves to the dominant, similar to the Italian version, but with a different voice leading due to the extra note.
The French Augmented Sixth (Fr+6)
The French augmented sixth, or Fr+6, is characterized by including the notes:
- Root (often the tonic or related pitch)
- ♭6 (lowered sixth)
- ♯4 (raised fourth)
- Optional ♭7 or other chromatic notes for color
This chord tends to have a more colorful sound, often used in Romantic and modern compositions. It resolves outward to the dominant, similar to the other augmented sixth chords, but with a distinctive harmonic flavor.
Comparison and Resolution
All three augmented sixth chords aim to create tension that resolves to the dominant. Their differences lie in the specific notes used and their harmonic color. The Italian is the simplest, focusing on the augmented sixth interval. The German adds a ♭3, enriching the harmony. The French introduces a more colorful palette with additional chromatic notes.
In practice, composers choose among these chords based on the emotional and harmonic context of their music, leveraging their unique qualities to enhance expressive power.