i - ♭III

The i - ♭III vamp is available as a chord in Dorian, but it’s not really a Dorian thing - it really belongs to modally ambiguous contexts, usually the Minor Pentatonic (1 ♭3 4 5 ♭7) (like “Stadium Rave/A” by Mark Governor) mode or what I call “Rock Minor” mode (1 2 ♭3 4 5 ♭6) (like “you should see me in a crown” by Billie Eilish).

You very rarely see a i7 - ♭IIImaj7 vamp, with fully-voiced-out seventh chords. That’s because i7 and ♭IIImaj7 are close enough to the same chord - ♭IIImaj7 is just i7 with its root moved up to a 9th. It doesn’t sound like you’re moving anywhere if you just vamp them. They sound like different variants of the same “tonic” sound. It can be a good technique if you want to basically stay on the same sound but change the color slightly, i.e. intentionally convey no real harmonic motion - but this is not a common harmonic device.

Instead you’ll see this vamp voiced as triads, and you’ll see it in rock music. Often that music will just be in minor pentatonic - no 2nd or 6th scale degrees at all. And just as often, a song will be in the Rock Minor mode, a 6-note mode which is the minor pentatonic with a 2 added, or from another perspective, the mode between Aeolian and Dorian (still no 6th scale degree). In fact, I tried to find songs in Dorian that vamped i-♭III, and every single candidate I found ended up being from either Minor Pentatonic or Rock Minor instead. I still think this is possible - a 6th would add a nice kind of brightness to a i-♭III vamp.

Instead, in Dorian, it's very common to see i - ♭III before some other chords, as part of a longer vamp, i.e. i - ♭III - ♭VII - IV. You'll see that in the next lesson. To me it feels like the most common purpose of a i - ♭III fragment in Dorian is a “launching” feeling - a gathering of energy one could describe as proactive, eager, interested.