Watch the A Form online guitar lesson by Brad Carlton from Guitar Lab: CAGED Modes
This lesson presents the Phrygian dominant mode over the A form of the CAGED system. Diagrams 10 and 15 show the A form arpeggio in red. The three notes that form this major arpeggio are: 1, 3, 5. The formula for the Phrygian dominant mode is: 1, b2, 3, 4, 5, b6, b7. If you view the arpeggio as a skeletal framework of the mode, you can then perceive the remaining four notes as color tones or chord extensions. These are presented in black. It is very important that you memorize the scale degrees and to aid you in this process you will learn to organize the tones in each position in terms of octaves.