D Ultraphrygian Scale
D Ultraphrygian contains 7 notes: D, E♭, F, G♭, A, B♭, C♭. It has 4 flats: E♭, G♭, B♭, C♭. The step pattern is H–W–H–W+H–H–H–W+H.
The most collapsed, darkest mode of the double harmonic family. The double-flat 3rd and double-flat 7th create a sound so compressed it blurs conventional interval expectations entirely.
The formula is 1, b2, bb3, 4, 5, b6, bb7. The bb3 is enharmonically a major 2nd, and the bb7 similarly challenges conventional notation. This extreme flattening creates unusual melodic ambiguity — what you hear doesn't match what the theory suggests on paper.
Primarily a passing texture rather than a sustained tonality. Use it for brief chromatic passages in avant-garde or contemporary classical contexts. The tight intervals sit in compact fretboard clusters that work for dissonant, atmospheric gestures.