Keys - Major and Minor Keys

The key of a song refers to its overall tonality dictating the melodic scale and the chords which occur therein.

Understanding this will aid you in working out the chord structure of songs and developing your own song writing skills.

Major Keys
There are 7 tones in each scale (key) and a chord can be built from every tone in the scale, therefore there are 7 chords. There are 3 major chords in each major key. If you look at the scale for each key, the major chords are dictated by the 1st, 4th and 5th notes in that scale shown by the examples below:

A song or chord progression will usually begin with the tonic (keynote) chord. For example, a song in the key of C will begin with a C chord; a song in the key of G will begin with a G chord and so on...

You'll also find minor chords in major keys. The most common minor chords in each major key are shown below:
There are no hard and fast rules about how songs or chord progressions can be composed but if you select chords from the same key they will always fit. Below is an example chord progression using chords in the key of C major:

C Dm F Em Am C G F

Minor Keys
3 minor chords are closely related in each minor key and most commonly occur in popular songs.

In the key of A minor, the Am, Dm and Em are the most important chords.

There are also 3 major chords in each minor key. In the key of A minor, major chords C, F and G occur. Again, playing these chords in any order will always work.