Great site! Just found it. Thanks 8 note!!
Hey, I've been playin guitar a while(30 years actually) but as you know that just gave me idiot status. Could someone tell me how come an Edim chord and a C#dim chord are exactly the same chord ?? Don't hurt me. Thanks

I remember once in a high-level jazz harmony class, a guy asked the teacher what was the tri-tone substitution, and the teacher sent him to elementary level… trying not hurt anyone, I’ll try to answer your question.

Well. The diminish chords are mainly built by 4 notes between the range of an octave. with 1 and a half step between each note… C, Eb, Gb, Bbb. Because Bbb means A. you actually play C, Eb, Gb, A. and because between A and C (C high octave) we have 1 and a half steep too, any of those 4 notes can be the root of the chord.

So by playing Cdim, we are playing Ebdim, Gbdim and Adim too. Now let’s transpose the four notes of Cdim chord half steep up, to C#.
We have now C#, E, G, Bb. It means that all this 4 notes can be the root of 4 different chords. Now we have the answer to your question C#dim and Edim share the same notes as well as Gdim and Bbdim.

Thanks man, I knew it was something simple lol! Seriously, I think I understand. Thanks for explaining it to me.