Minor 9th chords
The minor add2 and add9 chord, though similar to the add2 chord and add9 chord, adds a note to the minor chord. generally, it includes the first, the minor third and the fifth notes in its scale. You could get an madd2 or madd9 chord respectively by adding the second or ninth note
Take C minor as an example: C, Eb and G changes to C, D Eb and G (Cmadd2), or to C, Eb, G and D (Cmadd9). The notes differ while the notes remain the same and by that way, you could play madd2 when madd9 is mentioned.