Modal interchange: Dorian

Layering Dorian over Mixolydian is so common that it’s probably more common than Mixolydian alone. It’s extraordinarily popular with rock and funk. It gives your chord progressions a more 3-dimensional flavor, and keeps them from sounding too bright or goofy.

Dorian and Mixolydian are neighbors — separated just by the 3rd (natural in Mixolydian, flat in Dorian). But they’re also, as a pair, right at the exact center of mode-space. That is: at the highest level, you can divide modes into 1) modes with a ♮3 and 2) modes with ♭3, because the 3rd determines whether the root chord is major or minor. Mixolydian and Dorian together straddle that line.

And with Dorian and Mixolydian in particular, that means as a songwriter, if you’re in this modal space, and you want to make one section sound more major-ish and another more minor-ish, it’s just a matter of ♮3 vs ♭3. This can change note to note. Guitars can bend from one to the other. Some instruments can be emphasizing one and other instruments the other.

There are a LOT of ways to mix Dorian and Mixolydian. The number of really common ways, on the other hand, is a manageable about of material, and that's what I’ll cover in this lesson. Mixolydian typically functions more as the base mode, and Dorian as layered on top; there are songs that flip this, and have Dorian as the base and borrow from Mixolydian (e.g. Cantaloupe Island by Herbie Hancock), but I won't cover those here in this lesson.

The central question is: where does the ♭3 show up? How often do you use the ♭3 vs the ♮3? Frequently this is a melodic choice, and the idea here is that there's a spectrum here of where exactly you want to fall on the Mixolydian ↔ Dorian spectrum.

The two most important chords Dorian interchange gives you are a ♭III chord and a IV7 chord.

The ♭III chord

The ♭III chord is a major chord built on the ♭III. So, in G Mixolydian, that would be a Bb major chord.

The ♭III chord in minor modes (Dorian, Aeolian, Phrygian) gives you a characteristic power lift. Great for driving energy, and great for starting a phrase. Well, the thing is, Mixolydian can do that too, it just has to borrow the chord from Dorian.

You’ll see the ♭III interspersed into Mixolydian vamps we’ve already discussed. It’s usually combinations of the I, the ♭III, the IV, and the ♭VII. In the examples below I have them split into different orderings, which to me each feel like a different vamp with a different feel, but they’re all drawing from the same basic palette.

The I7 - IV7 vamp

This is the other main way a ♭3 makes its way into a Mixolydian tune: it turns the IVmaj7 into a IV7.

The I - IV vamp is weak in pure Mixolydian (stability issues, not distinctively Mixolydian), but when you add Dorian interchange, those problems go away, and it’s a completely different beast.

I’ll write this vamp as I7 - IV7 to emphasize the modal picture, but many rock songs voice these as triads. That’s just a matter of texture. In those cases, the sevenths will usually be implied in the melody or the guitar riffs. Voicing the sevenths explicitly just makes a song sound bluesier and more crunchy.

It’s important to notice here that a I7 - IV7 is exactly the starting vamp of a 12-bar blues.

What else does the ♭3 give you?

Minor pentatonic: if you borrow a ♭3, then you have all the notes you need for a minor pentatonic scale: 1, ♭3, 4, 5, ♭7 (all the rest are already diatonic to Mixolydian). Minor pentatonic melodies and riffs are idiomatic to rock, as a genre. And it’s not far from a blues scale, which is just a minor pentatonic with an added ♯4/♭5.

On the I7: a ♭3 gives you a ♯9 over this chord. (A dominant 7 sharp 9 chord is also called a “Hendrix chord”). It’s a great, harsh chord extension. It can be anywhere from really subtle (♭3 in the melody over a I triad) or a really explicit (guitar playing the entire I7♯9 with a distortion pedal).

Mode changes between sections: it’s common to hear an A section in Mixolydian and a B section in Dorian, or vice versa. Fundamentally this brings you from a major space to a minor space with just one alteration (so it doesn’t sound like you’re changing the energy a ton).

Vamps in this lesson

I have two Mixolydian vamps highlighted in this lesson.

• I - IV (which sort of becomes I7 - IV7)
  • There's a lot of songs that use this space
• I - IV - ♭VII - IV
  • This is just an example Mixolydian vamp to illustrate a general idea: Dorian interchange is common over any Mixolydian vamp.

I also have several vamps that use the ♭III alongside other Mixolydian chords.

• I - ♭III - ♭VII
• I - ♭III - IV
• I - ♭III - ♭VII - IV
• I - IV - ♭III
• I - ♭VII - ♭III - IV
• I - IV - ♭III - IV