#3
first they are both A chords..
now:
A add2 is just a normal A major,with the 2nd degree added (b note in that case)
the A2 is actually Asus2,you dont write A2 its just wrong.
Asus2 is adding the 2nd degree(b note again) but taking out the 3rd degree (whether is 3rd or flat-3rd)

to summarize:
Aadd2 : A-B-C#-E
Asus2 : A-B-E
#4
^ It might interest you to know that the rhythm sheet for Zappa's Rollo Interior, every chord was a sus2 chord, and every chord was notated A2, C2, ect.

Though, in answer to TS, X2 is a name for it, Xsus2 is far more common.
#5
Quote by Galvanise69
^ It might interest you to know that the rhythm sheet for Zappa's Rollo Interior, every chord was a sus2 chord, and every chord was notated A2, C2, ect.

Though, in answer to TS, X2 is a name for it, Xsus2 is far more common.



Probably to make it easier, but that isn't really correct notation, regardless of what Zappa did.
#6
Obviously, its a lot more widley known as Asus2.

I do however think its easier to take on the X2 name as an alternate naming.

Rather than seeing somone use that, and go "man I have no idea what hes on about"

You can go, yeah I know that, common to use Xsus2 but at least I know what your talking about.