From the recording Bright Morning Stars are Rising
This is a three chord tune, using the pinky to make the notes of the IV chord.... the chord built on the 4th note of the scale, and the middle finger to make the notes of the V chord, the chord built on the 5th note of the scale.
With the open string (1) and these two tones 4 and 5, you can make all the notes of the major scale. It shows why these three chords are so important for backing music.