Watch the 1 5 b9 Structures online guitar lesson by Brad Carlton from Guitar Lab: Open String Universe
This lesson uses a root fifth flat nine structure on the 5th, 4th and 3rd strings combined with the 2nd and 1st strings open. Voicing 1 is a Bsus add b9 voiced 1 5 b9 1 4. Voicing 2 is an E sus b9 voiced 1 5 b9 5 1. Both of these chords are subsets of the phrygian and phrygian dominant scales.