Second, the bass provides the rhythm of the music being played. This role is usually shared with the drums. Because it links the two functions of rhythm and harmony, the bass is often the instrument around which the rest of the music is organized. This lesson begins with a very brief discussion of chords, and then follows with a discussion of rhythm and how the bass defines it. Lesson 3 will take up the subject of chords in more detail.
All music is organized into chords.
A chord is a set of three or more different notes being played simultaneously, with one of the notes being the root note of the chord and the other notes defining the type of chord being played. The job of the bass is to indicate which chord is being played at a given moment, and this is most easily achieved by playing the root note of the chord. In each of these 8-measure patterns, an E major chord is played in the first two measures, a A major chord is played in the 3rd and 4th measures, a B major chord is played in the 5th and 6th measures, and the A major chord again in the 7th and 8th measures. First, it clearly indicates what chord is being played at any moment in the song, by playing only the root note on each beat. Other bass lines supply different rhythms using the root notes of the chords.