A neutral third is a musical interval between a minor third and a major third. Two distinct intervals may be termed neutral thirds. The larger one is an equal-tempered neutral third, which is characterized by a difference in 350.00 cents between the two tones, a hair larger than a ratio of frequencies between the two tones of 11:9. The smaller neutral third, called the undecimal neutral third, has a ratio between the higher-frequency tone to the lower-frequency tone of exactly 11:9. In music theory, an interval is the difference (a ratio or logarithmic measure) in pitch between two notes and often refers to those two notes themselves (otherwise known as a dyad). ... A minor third is the smaller of two commonly occurring musical intervals that span three diatonic scale degrees. ... A major third is the larger of two commonly occuring musical intervals that span three diatonic scale degrees. ... An equal temperament is a musical temperament, or system of tuning, in which an interval, usually the octave, is divided into a series of equal steps (equal frequency ratios). ... The cent is a logarithmic unit of measure used for musical intervals. ... Sine waves of various frequencies; the bottom waves have higher frequencies than those above. ...

Roughly speaking, then, neutral seconds are a quarter tone sharp from minor thirds and a quarter tone flat from major thirds. The equal-tempered neutral third may be found in the quarter tone scale and in some traditional Arab music (see also Arab tone system)). Undecimal neutral thirds appear in traditional Georgian Music. A quarter tone is an interval half as wide (aurally, or logarithmically) as a semitone, which is half a whole tone. ... A quarter tone is an interval half as wide (aurally, or logarithmically) as a semitone, which is half a whole tone. ... Arab music is the music of Arabic-speaking people or countries, especially those centered around the Arabian Peninsula. ... The modern Arab tone system, or system of musical tuning, is based upon the theoretical division of the octave into twenty-four equal divisions or 24-tone equal temperament, the distance between each successive note being a quarter tone (50 cents). ... Georgian music is characterized by polyphony, and accompanying haunting non-Western harmonies, which distinguish it from its neighbors like Armenia. ...

See also

• List of musical intervals
• Microtonal music