Lesson 19 · Part 5, A key is chords and scale together

Harmonising the scale

If you stack thirds on each note of a scale, you get the seven chords of its key.

The chords in C major

  1. ICCmaj7
  2. iiDmDm7
  3. iiiEmEm7
  4. IVFFmaj7
  5. VGG7
  6. viAmAm7
  7. vii°B°Bm7♭5

The chords of C major are C, Dm, Em, F, G, Am and B°. With a seventh added they become Cmaj7, Dm7, Em7, Fmaj7, G7, Am7 and Bm7♭5.

If you stack every other note of C major, starting from each degree in turn, these are the chords you get. Nobody chose them: each one is built from the scale's own notes, arranged in thirds.

Every chord, where it lives

ICiiDmiiiEmIVFVGviAmvii°B°
Open13151♭35113151♭31♭5
Fret 113151513511♭5♭3♭5
Fret 22fr131352fr151♭32fr133512fr1♭51♭3
Fret 33fr151353fr1♭3153fr15133fr1513513fr1♭3♭351
Fret 55fr151♭355fr1♭3155fr15135fr151♭3515fr1♭3♭3♭5
Fret 66fr13156fr1♭5♭3♭5
Fret 77fr133517fr151♭357fr131357fr151♭37fr1♭51♭3
Fret 88fr1513518fr1♭3♭3518fr151358fr1315
Fret 99fr131359fr1♭51♭3
Fret 1010fr151310fr151♭35110fr1♭3♭35110fr1513510fr1♭315
Fret 1212fr13351

The grid places seven chords across eleven home frets on guitar. Every chord is within reach from fret 2 and fret 7.

Read down a column to find one chord all over the neck. Each shape appears once, in the row for the fret it starts on. The line in the margin marks the rows your hand covers from a position where every chord of the key is within reach. In this key those positions are fret 2 and fret 7.

The chords of a key are not chosen one by one. They come directly from the scale.

Take each note of C major in turn, which musicians call the degrees of the scale, and stack two thirds on it using only notes the scale already contains. On C that gives C, E and G, a major chord. On D it gives D, F and A, which is minor, because the scale places a minor third above D. If you carry on, you get major, minor, minor, major, major, minor, and a diminished chord on the seventh degree.

That order is the same in every major key. It is why a song in C reaches for F, G and A minor rather than for chords outside the key, and why those chords sound as though they belong together. They are all built from the same seven notes.