Major third

A major third is the smaller of two commonly occuring musical intervals that span three diatonic scale degrees. The prefix 'major' identifies it as being the larger of the two (by one semitone); its smaller counterpart being, a minor third. The major third is abbreviated as M3 and its inversion is the minorr sixth.

The major scale is so named because of the presence of this interval between its tonic and mediant (1st and 3rd) scale degrees. Major chords too, take their name from the presence of this interval built on the chord's root (provided that the interval of a perfect fifth from the root is also present or implied).

A Major third in just intonation most often corresponds to a pitch ratio of 5:4 or 1:1.25, or various other ratios, while in an equal tempered tuning, a Major third is equal to four semitones, a ratio of 1:2^4/12 (approximately 1.259), or 400 cents, 13.686 cents larger. The older concept of a ditone (two major seconds=major third) is the pythagorean ratio 81:64 (1.2656= 1.125², two major seconds).

In the common practice period thirds are considered the most interesting and dynamic consonance along with its inverse the sixths, but in previous times it was considered an unusable dissonance. The Major third of a Major chord is what gives it its description as "happy", as opposed to the "sad" minor third of a minor chord. The Major third is considered the most consonant after the octave, perfect fifth, and the perfect fourth.

See also:

• musical tuning
• ditonus

Major third
# semitones	Interval class	# cents in equal temperament	Most common diatonic name	Comparable just interval	# cents in just interval	Just interval vs. equal-tempered interval
4	4	400	major third	5:4	386	14 cents smaller

External links

• Tonalsoft Encyclopaedia of Tuning