Hi all

I always think of sus chords as altered thirds, in fact I believe they are not considered to be either Major or minor, just chords where the third has been substituted for a 2nd or 4th in the case of sus2 and sus4.
As far as add 9 goes it is like a sus 2 but the third is in the next octave one octave higher than the sus 2.

Just my simple understanding.
Mike

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