Augmented sixth chord

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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, was further developed in the Baroque, and became a distinctive part of the musical style of the Classical and Romantic periods. 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.

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