Once the key is settled, so are the chords you are likely to use. Learn seven and you can read the harmony of most pop songs.
Chapter five established that the C major scale is seven white keys. Take each of those seven as a starting point and stack using last chapter's rule — skip one, three notes. Seven chords come out.
Hear all seven
Every one of the seven below is built from white keys only; not a single black key is involved. Play them in order and you will hear bright ones, dark ones, and one that refuses to settle.
- CC — home in this key
- DmDm — slightly dark
- EmEm — dark
- FF — bright, opens up
- GG — wants to return home
- AmAm — wistful
- BdimBdim — unstable
The chords you can build using only the notes of the key. In C major, that means the seven you can stack from white keys.
What happens when you go outside the key
Stay inside the diatonic set and the harmony hangs together. Bring in a chord from outside and that spot lifts off the page. Neither is better — it is a tool for the moment you want attention.
- All inside (C, Am, Dm, G)
C | Am | Dm | G
- Third chord outside (C, Am, A♭, G)
C | Am | Ab | G
In the second one, the third chord makes you look up. That is the effect of a note from outside the key. Chapter 16 covers how to use it on purpose. Getting comfortable with the six inside comes first.
Generate over a strictly diatonic progression. Because the foundation stays inside the key, wrong-sounding notes are much less likely.
Generate over an in-key progressionA key contains seven chords, and you can write endlessly with just those. Notes from outside are for when you want something to stand out.