Modal interchange: Aeolian

Mixolydian will sometimes borrow chords from Aeolian, too. This is a bigger borrowing move than we’ve seen so far: Aeolian interchange means borrowing two notes at once, the ♭3 and the ♭6. There are two core Aeolian chords that contain both borrowed notes: iv7 and ♭VImaj7. As you’ll learn in the Aeolian tutorial, these chords are substitutes for one another, two faces of the same sound. I think of iv7 as being pretty dark and serious, while ♭VImaj7 is more dramatic and powerful.

The first set of examples shows a couple different ways musicians borrow iv7 and ♭VImaj7.

The second set of examples shows the most common modal interchange pattern: the ♭VImaj7 - ♭VII - I vamp. This is sometimes known as the “Mario cadence”, coined in 2011 by Jason Brame. However, it more often shows up as a vamp (looping) than a cadence a.k.a. turnaround (one-shot, phrase ending), so I’m calling it the Mario vamp instead.

The Mario vamp builds energy. Each chord ratchets momentum, and the arrival on I feels like a resolution, so that's why it also works as a turnaround.

You'll also frequently hear the Mario vamp land on a V chord before returning to I, which is stacking Aeolian and Ionian interchange. This lets it really act as a turnaround.