Major Sixth

A major sixth spans six letter names and nine half steps: C up to A, D up to B, F up to D, G up to E. Abbreviated M6, it measures 900 cents in equal temperament.

▶C–A0:06▶G–E0:06▶F–D0:07

Counting it

C–D–E–F–G–A is six letters, so C–A is a 6th. For the size, think "an octave minus a 3rd": C up to the next C is 12 half steps, and A lies a minor third (3 half steps) below that upper C. So C–A is 12 − 3 = 9 half steps, a major sixth.

Four white-key 6ths are major: C–A, D–B, F–D and G–E. The other three (E–C, A–F, B–G) are minor; raise the top note by a half step to make them major (E–C♯).

Where you hear it

• A rising major sixth opens "My Bonnie Lies Over the Ocean" (on "My Bon-") and the three-note NBC television chime.
• In a major key, the 6th degree lies a major sixth above the tonic (A above C in C major).
• Adding a major sixth to a major triad gives the added-sixth chord C6 (C–E–G–A), a favorite final chord in swing.
• The major sixth above the tonic is the characteristic note of the Dorian mode (B in D Dorian), where natural minor has a minor sixth.
• Like thirds, sixths sound good in parallel. Two voices moving in parallel sixths are a staple of duets and of four-part harmony.

Consonance

The major sixth is an imperfect consonance in classical theory. Its pure tuning ratio is 5:3; the equal-tempered major sixth is about 16 cents wider.

Inversion and look-alikes

Inverted, a major sixth becomes a minor third: C–A becomes A–C, and 9 + 3 = 12. The same keys spelled with seven letter names form a diminished seventh, as in B–A♭, the outer interval of the diminished seventh chord B–D–F–A♭.

Practice with The 6th, the 7th & the Octave and Hearing intervals.