HELP understanding this chord progression?

Harmony & Theory
#1

The chords are:

E7 - A7/C# Am6/C
E7 - A Am/C

I’ve been playing over it, and even though I like what I hear, I would feel 100% comfortable knowing the reason why those chords are in there (I’m just beginning to seriously study some harmony).

Highly looking forward to read what you guys think about this progression.

Update: After a few bars the tonal center changes.

The whole thing looks like this:

(E major specified in the key signature)
E7 - A7/C# Am6/C
E7 - A Am/C

(A minor/C major specified in key signature)
Am7 - Bm7 Bbm7
Am7 - D13sus2

Cmaj7 - Dadd11
Cmaj7 - D13sus2

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#2

First part is a I - IV - iv progression in E major with the Am borrowed from E minor. Why does it sound good? Here’s the fun part! That Am6/C is a jack-of-all-trades chord. The ivm6, iim7b5 are inversions of each other and if you slap a b7 in there you get bVII9:

Am6

All of them act as V7 chords since they are practically the same as a V7b9 chord (B7b9) without the root. They have three notes A, C, and F# notes in common, four if you include the E to make it B7b9(11). B7b9 is an inversion of F#dim7:

image

The iv and bVII7 are very common in popular music. Together they’re known as the backdoor progression in jazz https://en.wikipedia.org/wiki/Backdoor_progression

I’m going to assume that the E7 chord would be played inverted with the 7th on top so the bass is descending D - C# - C. Both the A chords are inversions with the 3rd in the bass.

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#3

This section is really cool. The Am(7) is played again to establish the key change. The Bm7 - Bbm7 - Am7 continues the the chromatic descending line from the first part (D - C# - C). Then it moves up a fourth back to D and then vamps between fancy C and D7 chords (III - IV7). C is an inversion of Am7 so right there is your backdoor progression. Am7 - D7 - E = iv7 - bVII7 - I.

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#4

Put the 7th on the bottom of the E7 and you get a chromatic descending bassline.

Plus the flat 7th in the bass with a regular major triad above it is a really good sounding way to play a 7 chord on guitar in my view, for me it removes a certain “goofy” aspect I’ve always found in the guitar 7 chord voicings with the 7th chonking away in the middle of the chord.

edit: Hang on, I meant 2nd inversion triad over the flat 7.

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#5

Thank you so much, Ian. You open the door to a whole new world to me!
Since I read your answer two day 3 days ago I’ve been learning and researching about this “backdoor progression”, and I realized that there are many many many many common progressions that are worth learning in order to develop a vocabulary of common progressions I can improvise over.

Thank you so much!

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