Sixth

A major 6th chord is identical to the minor 7th of the relative key (albeit in a different inversion)

• ex. C6 is the same as Am7
• writing a chord as 6th instead of the equivalent 7th is obscuring the harmonic quality of the chord, making it more difficult to know which notes belong.
  • there is one exception to this, which is dependent on the context. Imagine we play a Cmaj7 chord, then drop the 7th to a 6 to play a Cmaj6 chord. In this context, the C still feels like the tonal centre (as it did with the Cmaj7 chord). In this case, it's more appropriate to think of that 6th chord as a 6th chord and not a 7th of the relative key.

When specifying a minor/major 6th chord, the minor/major refers to the 3rd scale degree (meaning the 6th note is the same in both, which is equivalent to the 6th scale of the major scale)

• ex. in a Am6 chord, the "m" still refers to the minor third, as in a standard Am chord. The 6th refers to the F♯, since that is the 6th scale degree of the major scale.
  • if we had used the minor 6th (F♮), then we would have a half-diminished chord. This changes the relationship with the chord's fifth (E) and gives it a more dissonant sound.

6/9 (aka 6add9)

Major

Cmaj6/9: 32223x

It is not a tense chord, and therefore doesn't require resolution.

Considered a substitute for the tonic in Jazz

Minor

Cmin6/9: 32233x

Evokes the dorian mode

Also considered a substitute for the minor tonic in Jazz.

shape on guitar