Robert Johnson -- Guitar and Vocal

Notice the fluctuations in rhythm; at times the rhythm almost stops. No matter what problems may occur in the performance, there is always some activity to carry the music forward. Johnson reduces the activity on the guitar to a few sparse notes while singing the first part of each phrase. At the end of each phrase, the guitar becomes more rhythmic while he improvises melody and words to fill the gap between phrases. The musical fills are free and often show some of his best technique.
Notice the slowly changing chords. The three simple blues chords are relatively easy to play on the guitar and can be strummed or broken into single notes to create activity below the melody.
