Originally posted by SLY
Hmmm, I'll try to explain.

let's take the B diminished

B D F G# , right? ... how about playing it endlessly?
B D F G# B D F G# B D F G# ....
as you can see , this chord can be called B diminished, D diminished , F diminished or G3 diminished .... and it's still one chord , got it??

I may not be following you on this, but B diminished is ONLY THESE NOTES IN THIS ORDER B, D, F. Adding the G# makes the chord Ddimadd6. Another thing, if you uses inversion of that chord say 3rd inversion, D, F, B. Yeah, it is still Bdim in the key of C major. The Roman Numeral would be a vii (small zero may be next to it) with a small 6 beside it. Now where it becomes off is when the notes B, D, F can be interpetted as D diminished, or F diminished. I'll try to show you, D diminshed would be the notes D, F, Ab. Yeah Ab and G# are the same note but when naming chords, the correct way to write D diminished is D, F, Ab because of the formula for the diminished chord which is 1-b3-b5. It's a very small error, and unless you go into extensive music theory you would never know. Same with the F diminished which is F, Ab, B. You probably understand now, more explaination of why it is that way would just be too long.