Learn Maybelle Carter's Bass Note Technique
Since each note of a diatonic major scale belongs to more than one chord within a key, each note can serve as a bass note for several different chords in that key. Take a look at B, the third note of the G scale: it’s the root of a Bm chord, but it’s also the third of a G chord, and the fifth of an Em chord. Looking at bass notes this way gives you some flexibility to begin working melodic lines into the otherwise-basic chord progressions in the Carter Family repertoire. Example 7a shows a G–D–G–C progression in 3/4 time with root bass notes. This root-bass approach provides a sensible and reliable way to play the progression, but that doesn’t necessarily mean you should stop there. Compare Example 7a to the ascending bass line in Example 7b. Here, we’re playing an A bass note (the fifth) under the D chord and a B bass note (the third) for the second G chord.
Excerpted from Carter-Style Guitar Basics: Creating Basic Bass Melodies