Sixth Chords - Is formed by adding a sixth to either a major or minor triad. For example to form a C6 chord you will start on a C major triad which is C-E-G, then you add the major sixth which is A. So C6 = C-E-G-A. For a minor sixth chord the principle is the same but you will construct if from a minor triad. For example to form a Cm6 chord you will start on a C minor triad which is C-Eb-G, then you add the major sixth which is A. So Cm6 = C-Eb-G-A. To simplify, the formula for a sixth chord is the 1st (root) + 3rd + 5th + 6th notes of a major or minor scale.
Ninth Chords - Is formed from either a dominant 7th, major 7th or minor 7th chord by adding the ninth. There are three commonly used types of ninth chord:
- Dominant 9th Chord (ex. C9) - Formed by playing the 1st + maj 3rd + 5th + flat 7th + 9th. Simply put, you start with a dominant 7th chord then add the 9th.
- Major 9th (Ex. Cmaj9)- Formed by playing the 1st + maj 3rd + 5th + maj 7th + 9th of a major chord. In other words you start from a major 7th chord and then add the 9th.
- Minor 9th (Ex. Cm9) - Formed by playing the 1st + min 3rd + 5th + flat 7th + 9th of a minor chord. Simply put, you start with a minor 7th chord then add the 9th.