I am close to completing Guitar Fundamentals 2 and may have missed something in an earlier lesson. The video "BARRE CHORDS LOVE THE 'MAGIC L'!", Lisa is talking about the first six chords in the key of G. These are: G, Am, Bm, C, D, Em. What is the music theory behind this progression? I'm a logical kind of guy and like to understand - not just memorize.