In addition, the circle of fifths plays a major role in harmonic motion. The most significant harmonic motion in western music is the cadential motion from V to I. Most tonal music travels on a harmonic path that eventually ends with this cadence. The V chord contains two elements that cause a musical tension that our ears automatically wish to resolve (to the I chord). First, the third interval of the V chord is the leading tone of the key. Our ears tend to want to resolve this pitch to the tonic. In addition, the tonic of the V chord is one step away (within the circle) from the tonic of the I chord (the key). This means that the seventh of a V7 chord is the flat version of the pitch that creates the difference between the key signature we are in (I) and the next key signature in the circle (V). If that pitch is raised half a step we are now in the next key of the circle (V becomes I). When that pitch remains lowered our ears perceive a flat leading tone that does not resolve to a nonexistent key within the same chord that contains the actual leading tone is the leading tone of the actual key.
Simple forms of music capitalize on this harmonic relationship by making it the only component of harmonic motion. This is true in both major and minor keys, however, I will focus my explanation on major keys for the sake of simplicity. Many pop, rock and folk songs only contain the chords I, IV and V. The IV chord is not only a fourth above the I, but also a fifth below. Traveling from the I to the IV creates a fake sense of cadential V-I movement. This is followed by movement from the actual V back to I. Another option is to travel from I to ii. The ii chord is a fifth above the V chord. Therefore a ii-V-I movement creates a sense of falling fifths. This sense can be further expounded by use of the vi chord. The vi chord is a fifth above the ii chord. A I-vi-ii-V-I progression creates an even longer sense of falling fifths.
More complex forms of music use this fifth relationship to temporarily travel to other key centers. These are the types of progressions that are found in soul, gospel and jazz music. I will discuss them in next week’s blog entry.