Hi SBM.

I know that you are on the road to learning music and music theory. I don't know if you've ever come across the information below. If you have just ignore it. If you haven't, maybe it will give come more insight into music for you.

One of the ways that diminished chords work is that they can be considered to be a 7th chord without the root note.

E7 = E G# B D

If the root note (E) is removed, the chord becomes G# B D = G#dim (a diminished triad).

Bdim7 = B D F Ab (where Ab is just another way of writing G#). Because the distance between each note in a dim7 chord is 3 semitones, there are really only three dim7th chords. They're just notated differently.

What I mean is...

Bdim7 = B (up 3 semitones) D (up 3 st) F (up 3 st) Ab (up 3 st) B (I'm back to the root note)
This chord is the same notes as E7b9 (E G# (or Ab) B D F) without the root. In the key of C major, E7b9 will often sound better because the key has F in rather than the F3 that's found in E9.

So Ddim7 = D (up 3 st) F (up 3 st) Ab (up 3 st) B (up 3 st) D
These are exactly the same notes as Bdim7. It's just the root note that is different.

The bottom line is that in a diminished 7th chord, the dim7 of each note in the chord contains the same notes.

So...
Bdim7 = Ddim7 = Fdim7 = Abdim7
Cdim7 = Ebdim7 = Gbdim7 = Adim7
C#dim7 = Edim7 = Gdim7 = Bbdim7

Therefore E7/B, G#dim/B, Bdim7 (and also Ddim7, Fdim7, Abdim7 since they are enharmonic equivalents of Bdim7) are all good chords that can be interchanged with one another to create a slightly different musical texture while preserving the harmonic movement.

I hope this helps with understanding why different people have arranged it in different ways.
--Noel

MY SONGS...
Audiophile BIAB 2025