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 a D6/9 no 3 voiced 1 5 1 9 6 9. Ionian, lydian, mixolydian, dorian and overtone apply. Voicing 2 is an Esus2 voiced 1 5 1 9 5 1. This chord is a subset of Ionian, dorian, lydian, mixolydian, aeolian, overtone and mixolydian b6 scales.