A modal mixture is a music theory concept that seems impossible to grasp without intimate scale knowledge. Truth be told, it is, but that doesn't mean you can't dip your toe into it. You may have heard the term "borrowed chord" before. That's fine, but the trouble with borrowing a chord is, who did we borrow it from? How can we give it back? Do they have any other chords we can borrow?
That's exactly what we're going to do. Look at the theory!
We shall not be diminished!
Ok, so why do modal mixture at all?
The most effective use of modal mixture for beginners is cleaning up the harmonic structure and getting rid of the viio chords. Who wants the sound of a viio in their chord progression? For our purposes, let us suppose that no one does. This is why a changing the viio to a VII chord is so popular. But where does that chord come from? How did people know to flat the 7th note, and turn the viio to a VII chord?
There are several modes that contain VII but, by far the easiest to remember is Mixolydian. Mixolydian mode is built off of the 5th scale degree of a major scale. The notes in Mixolydian mode are different from the major scale it is built off of by one note. A flat 7. Flat the 7th note in any major scale and you are now in Mixolydian mode.
C Mixolydian C-D-E-F-G-A-Bb
Why not use Mixolydian then?
Well, for starters, that would be using a mode and not a modal mixture. Also if you use Mixolydian you don't solve the problem of the pesky viio chord. You move it somewhere else (iiio).
Mixolydian is different from the major scale by one note, but it has a completely different harmonic structure.
I | ii | iii | IV | V | vi | viio
I | ii | iiio | IV | v | vi | VII
All we're going to do is borrow the VII from Mixolydian ONLY when we're playing the chord. Which means our iii chords can remain the same, and the rest of our harmonic structure will remain the same.
Our Mixed Mode:
I | ii | iii | IV | V | vi | VII
Voila, no diminished chord.
FINE, Now what?
Make a nice chord progression out of it! Duh!
Personally, I think to go from the iii -> VII sounds quite pretty. No doubt you will instantly recognize this sound.
Try this out:
I - iii - I - iii - VII - vi - V - I
How about some Mark Mothersbaug:
IV - VII - V - I
Or go for some Portishead:
iii - IV - iii - I - vii - vi - VII - vi - V
Wait! What's that vii doing in there!? Where did that come from!!
Muahaha! From the power of modal mixture! Ultimate Harmonic Power! See if you can figure out which mode contains a minor chord on the 7th degree!
Hint: Which mode contains a #4 degree?