Hi NoQuestion.
I'm having a bit of trouble understanding the question, but let me see if I can help:
The word 'third' can mean a few different things in music. The most common use is to describe intervals -- the distances between any two notes. There is a 'major third', which is the distance between the first and third note of the major scale, which is two whole steps, or four frets; a 'minor third' is the distance between the first and third notes of a minor scale, which is smaller by one semitone.
Another meaning of the word 'third' is when referring to harmony. Harmony lines can be 'a third above' the original line, meaning that the new line uses notes three
scale degrees above the notes in the original line. You can then add yet another line one third above that ... three part harmony, all lines a third apart.
Check this lesson for more.
In your example, when you say 'open G and B', do you mean the notes G and B, or the chords? If you mean notes, they are a third apart; if you mean chords, perhaps he means play a G chord with a B note as bass note? That can be described as a 'G chord over its third'.
I need more detail ... can you tab it out? Can you listen to the DVD again and let me know exactly what he says in what context?
We will get to the bottom of this
