Borrowed chords employ chords from the parallel key. For example, if you're in C major, the parallel minor key is C minor. This is not to be confused with the term “relative minor.” Relative keys refer to keys that share the same sharps and flats in their key signatures. For example, F major and D minor are relative keys not parallel keys.
Borrowed chords can add excitement to any chord progression. Unlike some of the other chords discussed in this chapter, borrowed chords don't merely enhance a chord. In other words, they are not harmonic extensions or alterations like sevenths or sharp fives, etc. Instead, borrowed chords bend the ear in another direction entirely. When they are used, the music shifts gears altogether, taking the listener in an unanticipated harmonic direction. You might think of borrowed chords as musical portals into another key center.
Flat VI and flat VII chords are wonderful examples of borrowed chords. Figure 6-12 shows an approach to C major (I chord) using both the flat VI and the flat VII. In this example, diatonic VI and VII chords from C minor are used.
Figure 6-13 shows two minor iv borrowed chord progressions. Again, the minor iv comes from the parallel key not the relative key. In this instance, the two keys used are C major and C minor.
FIGURE 6-12: Borrowed chords
FIGURE 6-13: Minor iv borrowed chords
Experiment with your own progressions using borrowed chords. Make sure the borrowed chords act as an unexpected musical deviation. Then resolve it to the original key. If you don't return to diatonic chords, your music will simply wander without direction.