OK, Since its Topical- that Epic Am blues has an E7 which is not consistent with harmonizing the Am.  What't the concept that allows for sticking in that tension?  Really works well, and I think I just saw the same on the chorus in Allman Brothers "Ain't wasting no more time."

I guess I asking how to know when to think outside the box for techniques.  

The concept is secondary dominant. A secondary dominant is used to lead back to the 1 chord.

This is accomplished through creating a dominant chord a fifth above the chord of resolution; the old V-I(i) resolution. 

Secondary dominants can resolve to any chord, but the chord it's leading to is usually the new 1 chord. This could be a temporary key change, it's pretty common.

Did I explain that well enough?

I should try to make a video on this with some examples. 

Yeah, that was on the money, short and simple.  I was afraid it was going to be more of, "well, it just kinda works."    This does seem to be fairly common technique and it works really well.  Maybe a demo of some ways it manifests would be good.

Gracias!

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