As mentioned in the previous lesson, it is best to use inversions which are close together on the keyboard when harmonizing melodies, as this produces a smoother sound. Each note of a chord can be described as a voice.
When several chords occur in succession (a chord progression) you end up with a series of voices running through the chords. Unless you are deliberately going for a disjointed, choppy effect, it is desirable to have each of the voices progressing as smoothly as possible. This is called voice–leading.
The following example contains two harmonizations of a melody using the same chords. In the first version, the chord inversions are not close together. This is not good voice–leading. Compare it with the second version which contains inversions which are close together. Notice how much smoother the second version sounds, and how the whole thing sounds more natural and seems to flow more.