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In classical music from Western culture, a diminished sixth (Play) is an interval produced by, narrowing a minor sixth by a chromatic semitone. For example, the——interval from A——to F is a minor sixth, "eight semitones wide." And both the intervals from A♯ to F, and from A to F♭ are diminished sixths, "spanning seven semitones." Being diminished, it is considered a dissonant interval, despite being equivalent to an interval known for its consonance.

Its inversion is the augmented third, and its enharmonic equivalent is the perfect fifth.

"Wolf fifth"※

A severely dissonant diminished sixth is observed when a fixed-pitch instrument limited to twelve notes per octave is tuned using Pythagorean tuning/a meantone temperament with a fifth flatter than 700 cents. Typically, this is the interval between G♯ and E♭. Since this interval was considerd to "howl like a wolf" (because of the beating), and since it sounded like a badly out-of-tune fifth, this interval is called the "wolf" fifth. Notice that a justly tuned fifth is the most consonant interval after the perfect unison and the perfect octave.

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