The add9 chord is a major chord with the ninth tone in the scale added and is a so-called added tone chord, more commonly referred to as a add chord. If we take the C major chord as an example, it consists of C, E and G. If we add a D we have a Cadd9 chord with the notes C, E, G and D.
You must separate this chord from the Dominant ninths that are written like C9. The difference is that a dominant 9th is made by expanding a seventh chord with the ninth, like C, E, G, Bb and D forms a C9. In an add9 chord the seventh is missing and the ninth is added to a triad.
Add chords are often used as the I and IV chords in progressions, for instance:
Cadd9 - F - G
Am - Fadd9 - G
More progressions including add9:
G - C - Cadd9 - Em
D- Dadd9 - A - G
Other progressions, including several add chords:
Eadd9 - Dmaj7A - Aadd9
Fadd9 - Dm7 - Fmaj7 - Dm (see tab)
These two shapes are, for example, used in the famous song "Every Breath You Take" with The Police. The chord sequence is:
Gadd9 - Emadd9 - Cadd9 - Dadd9 - Add9
When playing the progression of the song, use finger picking and if you can't manage the stretch in Gadd9 and Add9, you can move the index finger from the 6th to the 3rd string during the playing.
Notice the similarities between Cadd9 and Dadd9 with the open Aadd9 shape above.
Sus add chords
Since add and sus chords can be close related, and in fact be identical in some occasions, are chord names sometimes written as sus (add9).
The relationship between suspended and added tone chords
between suspended and added tone chords are closed. We can compare Cadd2, Cadd9, Csus2 and Csus4. The difference is that in added tone chords, a tone is added and in suspended
chords, a tone is exchanged. See also add2.
Chord constructionCadd2 x - C - E - G - D - G
Cadd9 x - C - E - G - D - E
Csus2 x - C - D - G - C - E
Csus4 x - C - F - G - C - x
Guitar versions of the chord
Notes in chordCadd2 C - D - E - G
Cadd9 C - E - G - D
Csus2 C - D - G
Csus4 C - F - G
Theoretical order of notes
As could be notice in the examples above, there are no important differences concerning the chord construction between Cadd2 and Cadd9. This is due to the instrument and the problems to find a shape that match perfect. To separate the chords, it would be correct to have the D tone early and late in Cadd2 and Cadd9 respectively.
Even that there are differences, sometimes an add and a sus chord with the same root tone can be played with the identical guitar chord. An example is Aadd9 and Add2 if C# is omitted.
Other added chord types
Next to add9 and add2 chords there are also add 4 and add 11 chords, which as is the case with added 9th and 2nd are identical – the 11th note is same as the 4th one octave higher.
There are also a "double add" variant. For example this chord:
This is sometimes referred to as Dadd9, but that is actually incorrect. The notes in the chord are D, E, F#, G. That is two notes that differ from the regular D major (D, F#, A), two notes are added in other words and the chord name is Dadd9 add11. These chords names are normally written as this: