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Posted by paige on June 12, 2001 at 08:56:14:
In Reply to: Jazz Chord Progressions posted by Clifton on June 11, 2001 at 17:48:10:
I have been playing/studying this Jazz Chord Progression of I-III7-vi-II7, (C-E7-Am7-D7)in the key of 'C.'
: My question is: "Where does the "III7 & II7" come from?"
the E7 (III7 in your example) is the V of the chord I would normally expect to see here. A really common set of changes would be I-vi-ii7-V7. So it looks like they left the vi chord (AM7) and preceded it with IT'S V7 (an E7). The E7, being the V to the Am7 is a strong chord to precede the Am7 with. They called it a III7 simply because you ARE in the key of C and they want you to know that though the chord is built on the the third degree of the C scale, it is to be a Major, not the minor chord you would ewxpect the III chord to be in the key of C. Truly, it is NOT the three chord in C, but is the V7 of the Am7 chord. This is a common invention - pretty nifty, isn't it?
Now - the D7 (II7) in the set of changes here.... again, whoever wrote these changes down did something that is sometimes called "shifting the key center". Basically, here is what happens:
You are in the key of C. Am7 is the vi chord in the key of C. However, anytime you see a m7 chord, it is either the iim7 of some key or can also be considered the vi7 of ANOTHER key. In this case, Am7 is the vi7 in the key of C. But an Am7 can ALSO be the ii7 for the key of G (the chord built on the 2nd degree of the G major scale). So for a brief time, the author of this set of changes "pretends" he is in the key of G, treating the Am7 as a ii7 chord, and then follows it with the V7 of the key of G - a D7. So the "key center" shifts during these two chords to "feel like" you are doing the ii-V7 from the key of G... then you are quickly dumped back into the key of C.
Hope that helps- there are any number of ways to look at this, and Jazz is replete with substitutions and variations. What I mentioned is my analysis of the chord changes... but the answer to your question "Where did the E7 and the D7 come from?" Could be as simple as the author saying "Hey, Bob! Listen to this - Doesn't the E7 and D7 sound cool? Let's do THAT!"
: In the Major scale the "iii & ii" are minor and in the minor scale the "ii" is diminished and the "III" is Major but, it is Eb!!
: Are there some rules that allow this to occur?
: Am I missing something? :^)
: Stay LOW, Live LOW & Play LOW,
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