Comma (music)
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In music theory, a comma is a small or very small interval between two enharmonic notes tuned in different ways. For example, an A flat tuned as a major third below C in just intonation, and a G sharp tuned as a major third above E, will not be exactly the same note. The difference between those notes, the diesis, is almost a quarter tone, easily audible.
All of the intervals mentioned below are presumed to be tuned in just intonation.
There are many commas, notably :
- Pythagorean comma or ditonic comma (difference between 7 octaves and 12 perfect fifths)
- syntonic comma, the difference between four perfect fifths and one major third plus two octaves
- schisma, the difference between 8 perfect fifths plus one major third and 5 octaves (equal to the interval between Pythagorean comma and syntonic comma)
- diaschisma, the difference between 4 fifths plus 2 thirds and 3 octaves
Commas are frequently used in the description of musical temperaments, where they describe minute tuning differences that are eliminated by that tuning system. For instance, twelve-tone equal temperament tempers out the Pythagorean comma by narrowing each fifth slightly.
