That's how I stumbled across this - I was trying to figure out some inversions.

Thinking about this more, I guess you can get clever creating a melody over these chords because they are vague in their definition - they are neither major or minor, and could fit in with a couple of scale keys since they can be named 2 different ways.

The circle of 5ths seems like it may have something to do with this as well since, using Asus2/Esus4 as an example, E is the 5th of A (in a C scale at least).

Yes, Christopher is definitely the resident expert on this stuff. Perhaps he'll chime in.

I'll check wikipedia too - good idea.

Thanks!
Rich