The Phrygian Mode is based around the third note of the major scale. In the key of G, this 3rd note is B. So this will be played as the B Phrygian Mode. To play the B Phrygian Mode you will start with the first note at the 6th string 7th fret. The Phrygian Mode sounds exotic and heavy. It's a very popular mode for many heavy metal bands like Metalllica and Slayer.