Myxomatosis

Tannin

I was sitting down just now tinkering with an old tune of mine from perhaps 45 years ago, written long before I knew any theory beyond what you learn in a few years worth of classical piano as a child. (Mayor and "minor" scales - by which they actually mean "harmonic minor" but nobody tells you that until some higher grade I never got to.)

Anyway, it mostly rocks between two major chords a whole tone apart (it has a couple of key changes but the riffs simply repeat in, for example, A instead of D).

D major is clearly the home chord, and these days I know that it is in D Mixolydian, rocking between D and C for the main part of each verse before going to Bb. Liker this:

D C
D C
D C
D C
D C Bb
D C Bb
D C Bb
Bb Bb D

All majors. Later on we do the same only using A, G and F, and sometimes other keys (if I feel like it).

Now the bit I'm confused by. D Mixolydian is the 5th mode of G major. That's clear enough. But when I go to the Bb I'm (if you want to think of it this way) borrowing a chord from G minor. 

How do we describe that? Is there a proper way?

viz

It’s a borrowed 6th chord from D minor. 

Loads of blues rock is written in mixolydian with the “b6 chord”, for example, Unchained by Van Halen. 

Btw, once you’ve established the home note of a song (in this case D), it’s not that helpful to refer to its relative Ionian mode, which has very little to do with it. Like you say, your song is “in D”, or to be more precise, D Mixolydian, and that b6 is borrowed from D minor.

Let’s hear it!

guitarjack66

I thought you were looking for Vetinary advice when I first saw the title.

Dominic

Seems like you're going down a Rabbit- hole to me