Watch the Add9 and Add11 Chords online guitar lesson by TrueFire from Acoustic Guitar Greatest Hits Vol. 1
Lesson Source: Matt Brandt's Chord Cookbook
When we leave the major or minor third in the chord and add the sus2 and sus4 notes, we end up with chords that have a different sound and name. Adding the sus 4 and leaving the major third gets you an add11 chord. Leaving the minor third and doing the same creates a minor add11. Adding the second note up from the root will create an add9 or minor add9. These numbers refer to the added notes one octave up.