Voice leading is what happens when several sounds within a harmonic movement move to the closest neighbouring note of the next harmony. In simpler terms: “Moving smoothly from one chord to the next.” This is desirable because harmony is meant to compliment the melody not distract the listener from hearing it. Voice leading started long before Bach but reached it’s height under the hand of Johann Sebastian Bach. Students of harmony will often be given the Bach Chorales to study how (mostly 4 voices – S-A-T-B) singing voices move to create a supporting harmony to a melody. Without voice leading randomly selected harmony would have notes sticking out in all sorts of conflicting places making the melody more obscured.
An example of voice leading to a simple melody
The following example has stepwise movement in the Alto and Tenor voices:
Chords can simulate a choir and sound best when played with the same kind of rules. Some simple rules include 1) Avoiding parallel 4ths or 5ths.
2) Resolving the note stepwise when possible. Moving from a dominant to a relative root 3rd rises and 7th falls a semitone.* see appendix