Lenny Breau, the brilliant Canadian jazz guitarist, was a great admirer of jazz piano master Bill Evans. One of the things he found in Evans’s playing was the use of sparse chord backing, which allowed a kind of “less is more” approach to arranging. Lenny moved it onto the guitar in his own unique way.
Here’s how it works: “7th” chords are made up of 4 notes: 1-3-5-7. They are commonly Major (1-3-5-7), Minor (1-b3-5-b7), or Dominant (1-3-5-b7). Note that the 1 and 5 remain the same in all 3 families. The 3 and the 7 denote the “color” of the chord (major, minor, or dominant), and are often referred to as the “color tones”, or “essential tones”. These three primary chord families often represent the larger ideas of motion (minor), tension (dominant), and resolution (major). The model for this idea is the “ii-V-I” progression. In the key of G, the “ii chord” is the Am7, the “V chord” is the D7, and the “I chord” is the Gmaj7. Played in that order, they cycle through motion, tension, and on to resolution.
The 3 and 7 often occur on adjacent strings, commonly on the D and G strings. They can occur in either order: “3-7”, or “7-3”. In cases where the 7 is on the bottom, the chords tend to have a darker, more ominous sound, and this facilitated the dark pallette on which Breau painted his impressionistic masterpieces. The video below shows some examples.