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Old 10-08-2017, 12:57 PM   #1
zanshin777
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Default Descending Secondary Diminished 7th Chords

https://youtu.be/r0XKX5Cy2vQ?t=1098 (Pinpointed Link)

Ex1

Dm7 - G7 - Co7 - Cmaj7 (ii7 - V7 - io7 - Imaj7)

Ex2

Dmaj7 - Bbo7 - Am7 - D7 (Imaj7 - biio7 - ii7 - V7)

I don't understand where secondary diminished chords are used there.

???
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Old 10-08-2017, 05:44 PM   #2
JonR
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Quote:
Originally Posted by zanshin777 View Post
https://youtu.be/r0XKX5Cy2vQ?t=1098 (Pinpointed Link)

Ex1

Dm7 - G7 - Co7 - Cmaj7 (ii7 - V7 - io7 - Imaj7)

Ex2

Dmaj7 - Bbo7 - Am7 - D7 (Imaj7 - biio7 - ii7 - V7)

I don't understand where secondary diminished chords are used there.

???
Co7 > Cmaj7 = "common-tone diminished";
Bbo7 > Am7 = passing chromatic diminished.

Neither of these are "secondary" chords (as I understand the term), although both are obviously chromatic.

These two moves are different from the more common "leading tone diminished", which derives from the vii in harmonic minor - they are not functioning like V7s of the following chord (because they don't contain a note a half-step below the following chord root). But both of them work via voice-leading - shared tones with neighbouring chords, and whole-step or (ideally) half-step moves up or down between those chords.

In fact the most common example of the passing dim7 is on biii of a major key. So Bbo7-Am would usually occur in G major, following either Bm7 or Gmaj7. It would be labelled (AFAIK)as biiio of the key, not biio of the Am7.
A famous example of this is in Cole Porter's Night and Day, on the line "near to me or far, no matter darling where you are", where chords (in key of C) run:
F#m7b5 - Fm7 - Em7 - Ebo7 (> Dm7)
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Old 10-11-2017, 07:33 AM   #3
zanshin777
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Co7 > Cmaj7 = "common-tone diminished";
Bbo7 > Am7 = passing chromatic diminished.

What are those terms?

Co7 : C-E-Gb-Bb
Cmaj7 : C-E-G-B

Bold letters are common tone the others lower 1/2 step.

Bbo7 : B-D-Fb-Ab
Am7 : A-C-E-G

B, D lower 1 step, Fb and Ab lowers 1/2 step.
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Old 10-11-2017, 12:19 PM   #4
JonR
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Quote:
Originally Posted by zanshin777 View Post
Co7 > Cmaj7 = "common-tone diminished";
Bbo7 > Am7 = passing chromatic diminished.

What are those terms?
They're both just simple descriptive terms.
"Common tone diminished" is a standard theory term:
http://www2.siba.fi/muste1/index.php?id=90&la=en
It's sometimes known as an "auxiliary diminished". It's defined as one note of the dim7 being the same as the following chord root.

But "passing chromatic" seems not to be a common conventional term. I mean, obviously this use of a dim7 is a passing chromatic chord, but then all dim7s could be described as that (except vii chords in minor keys).
A dim7 used that way just doesn't fit the two other possible ways a dim7 can move, which have distinct terms: "leading tone diminished" and "common tone diminished".

An example of it is given here, n the 3rd excerpt (Dbdim7 > Cm7)
https://tamingthesaxophone.com/jazz-passing-chords

One interesting view of this use is that it's the vii of the preceding chord. So in the above example you could see it as C#dim7, the vii of Dm. However, the voice-leading to Cm7 - or at least between the two chords - is the job the chord is actually doing, and any chromaticism always has to be analyzed according to where it's going, not where it's come from.

I'll check up on this unusual use of a dim7 and see if there is a more "official" term for it (google has not turned up much).

Quote:
Originally Posted by zanshin777 View Post
Co7 : C-E-Gb-Bb
Cmaj7 : C-E-G-B
Correction: Co7 = C-Eb-Gb-Bbb

The resolution is by semitone ascents, Eb>E and Gb>G. The Bbb (enharmonic with A), could remain as the 6th of C, or could descend to G or rise to the maj7 (B). IOW, the common-tone diminished ("cto" for short) works equally well, perhaps better, as a dim triad, without the 7th.
Quote:
Originally Posted by zanshin777 View Post
Bbo7 : B-D-Fb-Ab
Am7 : A-C-E-G

B, D lower 1 step, Fb and Ab lowers 1/2 step.
Yes, except it's F not Fb!
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