Hi,
The folloing progressions are from "Blues to Bechet" by John Coltrane.
I'd like know the role of Edim7 chord. I think it's a passing chord from Eb9 to Bb7.
Would anybody please let me know the harmonic analysis of this chord here?
Bb7 //// Eb9 //// Bb7 //// Bb7 ////
Eb9 //// Edim7 //// Bb7 //// G7 ////
Cm7 //// F7 //// Bb7 // G7 // Cm7 // F7 //
Thanks in Advance,
Alex
Ooh, ooh, ooh - Tom hasn't seen this one yet.
I reckon (and I've no doubt I'm going to be proved wrong in a very short space of time) that:
Bb7 -> Eb9 is V-I in Eb
Eb9 -> Edim7 is I - I#dim in Eb followed by
Bb7 as a substitute for Fm followed by G7 -> Cm which is a V7 -> I perfect cadence in Cm
So the Bb7 replaces the Fm in a iv-V7-i sequence. I was looking for II-V-I in this but it didn't work; maybe next time.
So, I reckon the movement is a key change from the key of E flat (3 flats) to the relative minor - C minor (3 flats) and the role of the Edim is instead of the common chord approach to key-changing.
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I'm thinking it's even simpler than that, Alan.
In a standard 12 bar blues, we'd expect to see Eb7, the IV chord, in m6. Instead we see Eº7.
Eb7: Eb-G-Bb-Db
Eº7: E-G-Bb-Db
With only one note different, it's a direct substitution for Eb7. (In my lesson on Chord Substitution this was substitution #8. Although I explained it differently - as a dim7 built on the 3rd of the original chord, if you check the spelling of the chord and the substitution, you'll see the result is identical: Gº7 = G-Bb-Db-Fb; Fb is enharmonic to E, so this can also be called Eº7)
In the context of the progression, this substitution has another advantage: voice leading. You have a single voice moving chromatically:
Eb is the root of Eb7
E is the root of Eº7
F is the fifth of Bb7
This voice leading idea continues in the next series, starting on a different tone:
Bb is the root of Bb7
B is the third of G7
C is the root of Cm7
You'll find these chromatic voice movements under many pleasing progressions, like the series of secondary dominants - for example, E7-A7-D7-G7-C7 contains this motion:
D is the 7th of E7
C# is the 3rd of A7
C is the 7th of D7
B is the 3rd of G7
Bb is the 7th of C7
This isn't random. The whole idea of chord progressions grew out of counterpoint - individual voices forming chords. Chromatic motion in any voice tends to give you a smooth progression.
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Thanks NoteBoat, Excellent!!!
