Every major key has a corresponding minor key. We call this corresponding minor key the relative minor. Every minor key has a corresponding major key. We call corresponding major key the relative major. Keys that are “relative” share the same pitches and therefore, the same key signature. This can be illustrated with the “circle of fifths”. The uppercase letters represent the relative major keys; the lowercase letters represent the relative minor keys.
To find the relative minor of a particular major key, the name the pitch a minor 3rd lower than the major key’s name. This will be the relative minor. Let’s try this. Find the key of ‘C major’ on the circle of fifth diagram above. The pitch of a minor 3rd lower than ‘C’, is ‘A’. ‘C major’ and ‘A minor’ are relative keys; neither of them contains any sharps or flats. Let’s try a next one. Find the key of ‘G major’ on the diagram above. The pitch of a minor 3rd lower than ‘G’ is ‘E’. ‘G major’ and ‘E minor’ are relative keys, they both contain one sharp (‘F sharp’).
Note: Everything mentioned above also works in reverse, that is, it works for finding the relative major of a minor key. To find the relative major of a particular minor key, name the pitch of a minor 3rd higher than that minor key’s name.
The other way to find the relative minor of a particular major key is by naming the sixth pitch of that major scale. For example, the sixth pitch of the C major scale is ‘A’. Therefore, ‘A minor’ is the relative minor of ‘C major’.
(Chapter 15 – Audio Sample 1)
(Chapter 15 – Audio Sample 2)
Although this way of finding the relative key is more difficult (as it involves memorizing every possible major scale), it makes the relationship between the relative major and minor keys very apparent. Both of the scales above are made up of the exact same pitches, and this is the reason that they share the same key signature. A song written in ‘C major’ uses the exact same pitches as a song written in the key of ‘A minor’. The only difference is that the song in ‘C major’ has ‘C’ as its tonal center, while the song in ‘A minor’ has ‘A’ as its tonal center.
Note: When using the scale to find the relative major of a particular minor key, name the third pitch of that minor scale. For example, the third pitch of the ‘A minor’ scale is ‘C’. ‘C major’ is therefore, the relative major to ‘A minor’.
In regards to the enharmonic keys from the preceding circle of fifth diagram. ‘A minor’ is the enharmonic equivalent of ‘B flat minor’; ‘D sharp minor’ is the enharmonic equivalent of ‘E flat minor’; ‘G sharp minor’ is the enharmonic equivalent of ‘A flat minor’.
Keys that have the same tonal center are called parallel keys. Because they share the same tonal center, parallel keys will therefore, also have the same letter name. Parallel keys do not however, have the same key signature. Here is an example of ‘C major’ and its parallel minor, ‘C minor’.
(Chapter 15 – Audio Sample 3)
(Chapter 15 – Audio Sample 4)
As you can see, both keys have the same tonal center (or root), ‘C’. All of the pitches have the same letter names, but three of the pitches are flats in ‘C minor’. The key signature of ‘C major’ and the key signature of ‘C minor’ will therefore, be different.
Relative and parallel keys are very important in music, because it is very easy to transition from major key to the relative minor key, or from major key to the parallel minor key.