Since I don't know music theory as well as many of you do, I probably shouldn't make a complete fool out of myself by posting these ideas. However, after studying the progressions, this is what I perceive...

Note: "nr" indicates Peter's terminology of no root or subbing one of the other chordal tones for the root.

C | Cdim | Dm7 | G | > Peter's Progression
C | F7b9/nr | Dm7 | G | > Peter's "nr" representation
C | F | Dm7 | G | > Simplified progression

C | Ebdim7 | Dm7 | G | > Peter's Progression
C | D7b9/nr | Dm7 | G | > Peter's "nr" representation
C | D7 | Dm7 | G | > Simplified progression

F | F#dim7 | C/G | A7 | > Peter's Progression
F | B7b9/nr | C/G | A7 | > Peter's "nr" representation
F | B7 | C | A7 | > Simplified progression

Conclusion: The Cdim7 family of chords are related to other chords in the key of C by altering basic chords into more interesting sounding chords.


JBlatz