Your own personal [four] and [five]

Remember that [one], [four], and [five] are the three chords at the heart of rock music.

I sometimes say that the [one] and [five] are rivals, perpetually battling each other for control of the musical space. And [one] and [four] are buddies, comfortable hanging out together.

Now, remember that every minor or major chord can be a [one] chord if we happen to be in the key based on the root of that chord. For example, the Dm chord is the [one]m chord in the key of D minor.

So think about this: every chord you use has its own rival (its own personal [five] chord) and its own buddy (its own [four] chord) close at hand. It's as if they're on speed dial on the chord's cell phone, ready to weigh in with their own opinion on any given subject at a moment's notice.

Let's look at this example using "personal [four] chords."

C - F/C C | - F/C C - | D - G/D D | - G/D D - |
F - B♭/F F | - B♭/F F - | G - C/G G | - C/G G - |

What's going on in this simple-sounding but complicated-looking chord phrase? At heart, it's this simple four-chord phrase:

C | D | F | G |

...but each of the chords makes a few side trips to its own personal [four] chord.

Now let's look at an example using personal [five] chords. In traditional music theory, these chords are called secondary dominants. They're dominant chords, but not of the main key that we're in.

C E⁷/B Am C⁷/G | F - C - |

In this example, E⁷ is the dominant chord from the key of A minor, and C⁷ is the dominant chord of F major.

Here's another example:

C⁷/E - F - | D⁷/F♯ - G - | E⁷/G♯ - Am - | D⁷/F♯ - C/G G | C

Notice how the bass moves upwards by half-steps. That kind of chromatic movement is easy to do with a combination of secondary dominant chords and chords borrowed from the parallel major or minor key, and it has a fun, ear-tickling effect. Unfortunately, this kind of chord writing is rare in most styles in rock music; you're most likely to find it from songwriters influenced by classical or jazz music.