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Plagal cadence confusion

Jonnysaxc

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I think I am confusing myself here and wanted a sense check please if possible?

As an example, in the progression:
F Major / F7 / Bb Major / Eb7 / Gminor / C7 / Fmajor

Eb7 is a plagal chord, and can be used instead of Bb Major, allowing the 7th note to descend a half step. Great!

In the book I am reading at the moment, it says "plagal can mean either IV or VII7 or both"
I am taking this to mean in the example given either Bb Major or Eb7

But, I am a bit lost here, doesn't a VII7 chord mean a half diminished chord?
 

BigMartin

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Forgive me if I'm misunderstanding something, but I've never heard of a plagal chord. A plagal cadence usually means IV-I in a particular key. So Fmajor / Cmajor would be a plagal cadence in C. I don't see any plagal cadences in the sequence you gave. Can you give us some more info?
 

Jonnysaxc

New Member
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Many thanks- I hadn't heard of it either and only know of plagal cadence as you describe.
I can see Eb7 as a substitute chord that is useful for the D it has as the seventh note but that is as far as my brain will stretch.
The book is George Bouchards Intermediate Improvisation, good book and clear- apart from this bit to me at least
 

BigMartin

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Still not with you I'm afraid. a bit more context might help.

Many thanks- I hadn't heard of it either and only know of plagal cadence as you describe.
I can see Eb7 as a substitute chord
Substitute for what?

that is useful for the D it has as the seventh note but that is as far as my brain will stretch.
The book is George Bouchards Intermediate Improvisation, good book and clear- apart from this bit to me at least
To be precise the seventh in Eb7 is a Db. So if the next chord was Ab or Abmaj7 (a perfect cadence), the Db would resolve nicely onto the C. But there isn't a C in the Gminor chord which follows Eb7 in the sequence you quoted.
 

Pete Thomas

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If there had been an F instead of that Gm7, and if the Bb had continued for two bars instead there being that Eb7 then yes, it would have been a plagal cadence.

In classical harmony a there is also an interrupted cadence, which is like a perfect cadence (V7 - I) except iot goes to a different chord than the I you expect, e.g. V7 - III).

So here, if there was a C7 instead of the Eb7, then that would be an interrupted cadence (ie you expect the F but get a Gm7)

bVII7 can actually be a substitute for IV7 or IVm (modal interchange), so in a obtuse kind of way you might thin of that as an interrupted substituted plagal. But that is getting quite advanced and probably way too convoluted to be worth considering.
 

Jonnysaxc

New Member
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6
Thank you to all very much, I meant to type Db as the flat 7th of Eb so made things even more confusing
I think I will look at this example in the theory book as "something else you can do if you fancy it and don't want to play on Bb major for two bars"
Trimmy, it is confusing because I made it confusing!

Cheers gents
 
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