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Old 12-29-2017, 05:32 PM   #1
zanshin777
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Default Secondary Diminished Chord Progression

They are given as an example of Secondary Diminished Chord Progression. However I don't get how they are Secondary Diminished.

Ex1

Key : C

Dm7 - G7 - Co7 - Cmaj7

Ex2

Key : D

Dmaj7 - Bbo7 - Am7 - D7
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Old 12-30-2017, 07:22 PM   #2
JonR
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I think you're right.

Ex1 is not a secondary diminished, it's a "common-tone diminished" (shares root with the following chord).

Ex2 is debatable. It could be the vii of the key (Bbdim7 = C#dim7, borrowed from D minor), or (leading to Am7) but I think technically it's another common-tone diminished, because it shares the E note with Am7.

A better term (IMO) for "secondary diminished" is "secondary leading tone chord", which clarifies that it has a vii relationship to the following chord - which neither of these examples do.
https://en.wikipedia.org/wiki/Second...s#Leading-tone

Where did you get get these examples? Not Rick Beato, I hope?
It may be that whoever used the phrase "secondary diminished" was using it to describe other uses of the dim7 besides the usual vii function - of which these two are good examples (common-tone diminished).

Examples of true secondary diminished chords could be F#dim7 before G7 in Ex1, and G#dim7 before Am7 in Ex.2.
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Old 01-01-2018, 10:35 AM   #3
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Sorry. I hadn't added the video .

Now I found and added. Here it is.

https://youtu.be/r0XKX5Cy2vQ?t=1045 (Pinpointed Link)
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Old 01-02-2018, 03:24 PM   #4
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I knew it! It IS that damned Rick Beato again!

He's just being lazy with his terminology (I mean lazy from a classical viewpoint).

As I guessed, what he means by "secondary" diminished is "any dim7 that is not the vii of the key."

IOW, the "primary diminished" would be the vii of the key (Bdim7 in C major or C minor). So any other dim7 has to be secondary - which I suppose is a reasonable use of the term, at least in jazz.
You can then differentiate (as he does) between ascending or descending ones.

Conventionally, however, the phrase "secondary diminished" refers only to the ascending type: the "secondary leading tone chord", a dim7 that is vii of the following chord.
The descending type (ie where the root of the following chord is a half-step below the root of the dim7) is really a form of the "common-tone diminished".

So, in his demo, Co7, which he calls (not unreasonably but wrongly AFAIK) a "tonic diminished", is a classic "common-tone diminished" (obviously because it shares the root with the following Cmaj7).
There is no way that's a "descending" dim7, so he's just put it under the wrong heading. Only one of the voices descends (A to G), the others (Eb-Gb) rise to E-G.

The Bbo7 which he calls "bii diminished", is a less obvious common-tone diminished - it shares the E note with the following Am7. It's common (as he says) as a biii chord, followed by ii.
Its use in Wave is unusual, however, in that the key is D, and Am is a secondary ii chord (of the approaching IV, G). So you could say Bbo7 is a secondary dim (biii of G) for that reason.

Still - taking a step back from all this jargon! - all you really need to know is the three ways a dim7 can be used. (And only 3 ways are possible).

1. vii of following chord. One note (any note) of the dim7 rises by half-step to the following chord root. This is the "leading tone dim7". If it's vii of any chord other than the tonic, then it's a "secondary diminished", or "secondary leading tone chord". Can resolve to a major or minor chord.

2. One note (any note) of the dim7 is the same as the following chord root. Common-tone diminished. Abbreviated in analysis to "CTo7".
Usually this moves to a major chord, typically the tonic.

3. One note (any note) of the dim7 descends by half-step to the following chord root. Sometimes called a "chromatic diminished" or "passing diminished"; but really (as I understand it) another form of the CTo7 (shares its 5th with the following chord).
Almost always used to lead to the ii of a major key, either from the tonic or the iii chord.

Remember there is no other possibility for a dim7, because the chord is symmetrical. If you see (eg) Fdim7, Ddim7 or G#dim7 leading to C, they are all just Bdim7 in different inversions, all acting as vii of C.

Last edited by JonR; 01-02-2018 at 03:33 PM.
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Old 01-04-2018, 07:01 PM   #5
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Understood.

Thank you very much JonR for your detailed answer.
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