The Am7 to C#dim7 to A7 leap

In Christopher Schlegel's 'A' Section Chord Changes, he presents the 1, 6 (#1dim7), 2, 5 forms, and then the alternate higher forms.

In the higher forms, he actually shows the A7 as an alternate for the C#dim7, which sounds great. My question comes when he explains that the C#dim7 is actually a substitution (the 7 of 2) for the original Am7 (6 chord). In effect, how does the higher A7 work to 'replace' the originally intended Am7? Their major and minor aspects seem to conflict (not in sound, but certainly on paper).

Mind you, everything sounds good, and I'm hardly questioning his judgement here—just trying to learn why/how this works.

Thanks!

ch:

Originally Posted by: find_ch...for the original Am7 (6 chord).

May have answered my own question. Wondering if the original Am7 was actually a A7.

Hey, there! Glad you are checking out my jazz lessons. :)

Originally Posted by: find_ch
In the higher forms, he actually shows the A7 as an alternate for the C#dim7, which sounds great. My question comes when he explains that the C#dim7 is actually a substitution (the 7 of 2) for the original Am7 (6 chord). In effect, how does the higher A7 work to 'replace' the originally intended Am7?

Good observation & question!

You've answered the question in the first line: it sounds good. :) But in more depth, an A minor chord is the naturally occuring chord in the key of C major. But in order to make it sound jazzy, I've included a modulation via a note that isn't part of the key (C#) and as a result a chord that's not in the key (A7 or A7b9 or C#dim7).

The first thing I did was to replace the C in the A minor chord with a C# because it's only a half-step from D, which is the root of the next chord.

a-c-e
a-c#-e

So, now we have an A major. Next, we can put a G in there to make it a fully dominant 7 chord, good jazzy sound & a great way to make a V7 of I (A7 to D).

a-c#-e-g

Finally, I can add a B-flat making an even jazzier sounding chord, an A7b9.

a-c#-e-g-b-flat

But, if I don't include the root note A, then another way of spelling this chord is C#dim7.

c#-e-g-b-flat

All of them are basically just a way of providing a voice-leading, dominant function way of getting to the next chord, the D minor.

I explain a bit more about this in the Intro to Jazz Rythm Guitar tutorial 3rd lesson.

http://www.guitartricks.com/lesson.php?input=21171&s_id=1697

And there is even more about how that sort of thing works in my Extended Harmony Chord tutorials.

Hope that helps! Ask more if necessary & have fun learning some jazz. :)

The C#cim7 is the same as an A7b9 minus the root.


So you are going from Am7, to A7b9, to A7, which will work nicely going in a circle of 5ths context to the next chord.


Also, because diminished 7 chords have no allegiance to any specific key because they are techincally 4 chords at once, you can use them to modulate almost anywhere and justify it.


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