The musical interval of a major sixth is the relationship between the first note (the root or tonic) and the sixth note in a Major scale. It is the inversion of the minor third. It can be produced by starting on a high note and playing the sixth below or by starting on a low note and playing the sixth above. It is abbreviated as M6.

A major sixth in just intonation corresponds to a pitch ratio of 5:3 or 1.6666. while in an equal tempered tuning, a major sixth is equal to nine semitones, a ratio of 1:2^9/12 (approximately 1.682), or 900 cents, 15.641 cents wider. The ratios of both major and minor sixths are the ratios of pairs of consecutive numbers of the Fibonacci sequence: 5 and 8 for a minor third and 3 and 5 for a major third, the golden ratio lying between the minor sixth and the major sixth.

In the common practice period, the sixths, along with their inverse, the thirds, are considered the most interesting and dynamic consonances. The major sixth is considered the most consonant interval after the unison, octave, perfect fifth, perfect fourth, and the major third.

See also:

• musical tuning
• minor sixth