Perfect fourth: Difference between revisions
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== In just intonation == | == In just intonation == | ||
The only "perfect" fourth in JI is the '''Pythagorean perfect fourth''' of [[4/3]], about 498 cents in size, which corresponds to the MOS category of the diatonic perfect fourth and is the octave complement of the perfect fifth of [[3/2]]. However, various "out of tune" fourths exist, such as the '''Pythagorean wolf fourth''' [[177147/131072]], which is sharp of 4/3 by one [[Pythagorean comma]], and is about 522 cents in size. | The only "perfect" fourth in JI is the '''Pythagorean perfect fourth''' of [[4/3]], about 498 cents in size, which corresponds to the MOS-based interval category of the diatonic perfect fourth and is the octave complement of the perfect fifth of [[3/2]]. However, various "out of tune" fourths exist, such as the '''Pythagorean wolf fourth''' [[177147/131072]], which is sharp of 4/3 by one [[Pythagorean comma]], and is about 522 cents in size. | ||
Other "out of tune" fourths in higher limits include: | Other "out of tune" fourths in higher [[Prime limit|limits]] include: | ||
* The 5-limit '''acute fourth''' is a ratio of 27/20, and is about 520 cents | * The 5-limit '''acute fourth''' is a ratio of 27/20, and is about 520 cents | ||