Watch the 1 5 1 9 Structures online guitar lesson by Brad Carlton from Guitar Lab: Open String Universe
This lesson uses a root fifth root ninth structure on the 6th through 3rd strings combined with the 2nd and 1st strings open.
Voicing 1 is an Asus2 voiced 1 5 1 2 2 5. This chord is a subset of Ionian, dorian, lydian, mixolydian, aeolian, overtone, mixolydian b6 and melodic minor scales. Voicing 2 is a Bsus2sus4 voiced 1 5 1 9 1 4. Ionian, lydian, mixolydian, dorian, aeolian and mixolydian b6 apply.