The Dominant Chord
In the previous section you learned about chord progressions in fourths.
What makes these progressions so compelling (and ubiquitous) is that they exploit the concept of dominance.
Dominant chords are something of musical magic. Like the two opposite poles on a magnet, the pull between two ends of a perfect fifth interval is one of the greatest forces in Western music. The interval of a fifth is actually a stable force when played as a harmonic interval, but it is a propulsive force when played in melodic succession from V to I. When diatonic triads or more complex chords are played in likewise succession, you can hear the same force that propelled classical composers like Haydn and Beethoven to obsess on this progression at the end of almost every piece composed in the classical and early Romantic eras.
Figure 5-9 illustrates the pull toward the tonic that the V-I chord progression exhibits. Here, this exercise is referencing both the pull of the fifth within each chord to its tonic and the pull of the V chord itself to the I chord.
The strength of the relationship between the tonic and fifth, and the I chord and V chord, is particularly important for budding musicians to understand. In general, remember that everything in music is relative and connected in some way. For example, the V chord has its own V chord (called a V of V), and the two can be paired up for additional harmonic color.
Hearing and feeling fifths
Notice that beat four in every bar contains the fifth of the following note.