In music, a ditone is the interval 81:64[1], which is 407.82 cents. It is the major third in Pythagorean tuning. The ditone is evenly divisible by two major tones (9/8 or 203.91 cents) and is wider than a just major third (5/4, 386.31 cents) by a syntonic comma (81/80, 21.51 cents).
"The major third that appears commonly in the [Pythagorean] system (C-E, D-F♯, etc.) is more properly known as the Pythagorean ditone and consists of two major and two minor semitones (2M+2m). This is the interval that is extremely sharp, at 408c (the pure major third is only 386c)."[2]
It may also be thought of as four justly tuned fifths minus two octaves.
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