augmented sixth chord

An augmented sixth chord is a musical chord that typically contains three or four notes. Its defining characteristic is that its two outer notes form an augmented sixth interval. This type of chord is often used to create harmonic tension and typically resolves to dominant harmony.1

Augmented sixth chords are altered chords, meaning they are built by chromatically altering notes from a standard chord. They are known for their dissonant and ambiguous harmonic function, which can blur the listener's perception of tonality.2

Common types of augmented sixth chords include the Italian, French, and German sixths, each with specific intervals above the lowest note. These chords became more prominent in the 19th century as composers explored harmony for its coloristic and expressive qualities.342