Dammit, I meant add2, not sus4. The thread should read: add2 = add9?

Anyways, I was formulating chords on a piano (because my head feels like it will explode when I do that on a guitar). I noticed that in any major key, a add2 chord sounds like the add9 chord in that same key. Am I simply not appreciating the difference due to my lack of ear training, or is that really the case?

Oops, I think it just dawned on me. Is it because a 9th scale tone is the second scale tone in the next higher octave?

Sascha