コードファミリー（英語）

Chords keys. Of more relevance to the guitar player are ‘chord families’, or the groupings of chords that go with the keys. This could be useful in knowing what chords actually sound good together.

This easy-to-understand theory will help you to compose your own songs, obviously, but not only this! You will have more tools to play those songs where you don't exactly remember the chords, or even to guess the chords of a song you like.

According to the C scale, each note can represent a specific chord in the key of C. Look at this chart of chords for the key of C:

Scales Looking at the major scales, we can easily know which chords will sound good with any chord. For instance, the first note of the C scale represents the first chord C (major). The fourth note, F, represents the fourth chord F (major). Some of them are major chords, some are minor, but the seventh represents a ‘diminished’ chord. Note that, between some notes, you have a whole tone difference (W) and in other cases you only have half a tone step (H). Look at the chart of the major scales:

Chords codification. Notice that, for chords, we typically switch our numbers to Roman numerals: uppercase for major chords, lower case for minor chords. So, we can see that the major chords are in positions I, IV and V. The minor chords are in positions ii, iii and vi. The seventh position will be diminished chords, but they are more difficult to play and we can leave them aside for later.

The outside circle of this diagram is made up of 12 letters - these correspond to the key that the music is in and comprise the root chord of that key.

The chords that exist on either side of the root chord sound great with that first chord. The chord that appears on the inside circle below the root chord is called the ‘relative minor’ chord. Minor chords sound more mellow or sad. These four chords will be enough for most of your song writing, but also look at the chords on either side of the relative minor - these chords, when used sparingly, will bring texture and interest to your writing.

Click here to view a whole chord families formation: Chord Families.