I have come upon a couple of tunes that use (as an example) an intro of Db-Bb-Ab-Gb and then. move to an alternation chord pattern of Eb-Ab. I have looked at modes, minor scales, etc. The puzzling part of this is that, in the key of Eb, the intro would start on a b7th and then move to a somewhat diatonic Bb-Ab before it moves to G (iii minor if diatonic).
Any thoughts/help would be most appreciated…hope I am not missing something painfully obvious! John
Hi @landermaestro , thanks for writing,
Can you send an example? Lead sheet or something notated would be fine 
Happy to help!
-Tuomo
Hi Tuomo, Thank you for the response…I have attempted to drag a portion of the lead sheet that shows this chord progression. While this is from ‘In the Midnight Hour’, I can send other examples. The best I have been able to come up with is that in Blues and Jazz/Blues, moving dominant chords around is pretty common and this tune simply ‘modulates’ to a different key after the introduction. Your input is valued and appreciated. John
Hi John, thanks for the example. There are several ways we can analyse these chords.
For example in the case of ‘In The Midnight Hour’, the intro can be explained with a phenomena called ‘modal interchange chords’.
‘Modal Interchange’ chords are chords that are “borrowed” from the same minor key, in the key of Cmaj, Cminor. In Cmajor/Cminor the modal interchange chords are Ebmaj, Abmaj and Bbmaj, as these scale degrees are within the Cminor scale:
So if you see major chords in a major key that are on scale degrees bIII, bVI or bVII, they are derived from the minor of the same.
This is also a common way to harmonise the minor pentatonic scale, as happens in the intro of ‘In The Midnight Hour’.
I hope this helped, let me know if you have any further questions!
-Tuomo
First, many thanks for the response. I remain a bit confused. If we stay within the C scale the intro is C to A (or A7) to G (or G7) to F offers two questions; 1. wouldn’t the A be Ab? the G be a G minor? and the F be F minor? Lastly, when the body of the song goes to D/G alternating chords is this simply a modulation? I really don’t mean to be a bother, but I am really trying to understand. Thanks in advance for your help. John
Tuomo…my bad. The ‘body of the song’ actually appears to be in the key of D major…thus, the question about modulation as the last chord before the D-G alternating starts right after the F (7) chord. Sorry for the confusion. John
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