A powerful consideration that affects the voicing of chords is the particular inversion that is being used. A chord has three notes, which means that it is possible that any of the three notes can be used to provide the bass note. When the root is in the bass, the chord is said to be in root position; when the third is in the bass, the chord is said to be in first inversion (also are indicated with a superscript 6); when the fifth is in the bass, the chord is said to be in second inversion (also indicated with a superscript 6/4). From root position to second inversion the harmony becomes less stable. The particular order of a chord’s notes is also referred to as that chord’s voicing. You can specify a voicing without writing all the notes by adding a bass note to the standard chord notation. You do this by adding a slash after the chord notation, and then the name of the note that should be played on the bottom of the chord.
When you employ inversions of orchestrated chords—chords assigned to different instruments in an ensemble—then you’re using a technique called chord voicing. The order in which the chord notes are played is quite important in an arrangement. If nothing else, the note that’s placed on top of the chord (the one played by the highest instrument or voice) is probably going to be heard more clearly than the other notes. In addition, the order of the notes and to which instruments they’re assigned affects the color and emotional tone of a piece. So it’s key that you learn the ins and outs of voicing.
Voicing becomes even more interesting when you’re working with extended chords. That’s because you have more types of inversions to deal with.