What is the difference in the 9 chord and add 9 chord?

The use of chord symbols or nomenclature is a source of confusion for musicians. The major chord consist of the three intervals: 1, 3, and 5. When you add the 9 interval to the major chord you have the add9 chord i.e. Cadd9. So what is the 9 interval? It is the same as a 2. In a one octave major scale you have the intervals 1,2,3,4,5,6,7, and 8. The 8 is the same note as the one. That is why it is called the octave. The 9 is the same as 2, 11 is a 4 and so on. An add 9 chord is simply a major chord with an added 9 (or 2) interval. An easy way to learn them is simply add the note that is one whole tone higher than the chord you are playing. For example, when playing the C chord just add the D note to the chord creating the Cadd9. You see this chord written as Cadd9, Cadd2, C2, Csus2, Csus9, C+2, C+9. The correct nomenclature is Cadd9. Sus is reserved for the 4 and the + is reserved for the augmented interval (which is a another lesson).

The C9 chord is very different. It is an extension of the dominant 7 gender. A C9 has the intervals 1, 3, 5,♭7, 9. Notice it has the ♭7 also. This gives the chord a very different sound than the Cadd9.

I hope this helps. Please post any comments or questions you have.

Keep pickin’!
Brian