DISCLAIMER:
A lot of this stuff is subjective and can be represented many different ways. This is just my thoughts on a useful way to analyze this.
Fremen said the notes played are: D, G#/Ab, A.
However, I transcribed this and the notes are actually:
D, G, A#/Bb, C#Db
https://soundcloud.com/causticatastrophe/freman-example
4 notes is not a lot to go off of, and therefore gives a lot of room for interpretation but this is how i see it:
The tonic sounds like it is D, sounds pretty resolved there. Even the second phrase resolves to D an octave down, reinforcing this. So it would make since to me to start here.
The characteristic change for Phrygian is the flat 2nd interval. That’s the only difference between it and Aeolean. This must mean that in order to be considered, the 2nd should be predominant in the melody/harmony.
Phrygian dominant’s 3rd is raised a semitone from the original Phrygian.
If we stick with the idea that D is the tonic, it cannot be Phrygian or Phrygian dominant.
D Phrygian:
D, D#/Eb, F, G, A, A#/Bb, C
D Phrygian Dominant:
D, D#/Eb, F#/Gb, G, A, A#/Bb, C
The Eb (the 2nd interval that is characteristic of Phrygian) is absent from play and as such lacks any expression that would indicate Phrygian. Also, both Phrygian examples lack the Db/C# that is played.
The only thing i can think of that would fit would be something like a D Harmonic Minor.
D Harmonic Minor
D, E, F, G, A, A#/Bb, C#/Db
With this in mind, the 2nd, 3rd, and 4th (E, F, G) could be different than above, so it can be several different things. Hell, it could be Tetratonic. The point here isn’t to be “right” since there are way too many directions this can go, but rather to show many ways this “can” go. D Harmonic Minor makes the most sense to me, based on what i perceive as a tonic of D. That’s the great thing about music, its an art, and art is about making people feel shit. Theory is just a way to attempt to deliberately, not accidentally do this.
This reminds me that I need to update my harmony chart to do the modes of harmonic minor. Since Phrygian Dominant is a mode of harmonic minor, it would have been easier to spot this.
Here’s the link to the one i did for the modes of C major: