Watch the Fourths online guitar lesson by Robbie Calvo from Double Stop Chops
Double stop 4ths also follow the same pattern as the other double-stops in that they adhere to the harmonized major scale. All of the 4ths are perfect fourths except for the augmented or sharp (#) 4 on the fourth degree. We'll see that this fourth will actually be found as the 7th double stop in the scale, giving us the major seventh of the scale. Sounds complicated, doesn't it? It is...but it'll make sense when you see it played out against the trIad and 7th chords in the scale. Let's take a listen!