Related Keys

1. Closely Related Keys

There are a total of 24 keys in music. 12 different pitches from C to B, each with major and minor, making a total of 24. Among these 24 keys, some are closely related, while others are more remote. In music theory, we technically term them Closely Related Keys (or “Close Keys”) and Distant Keys, respectively.

Understanding the relationship between keys is important and serves as a hint when modulating or temporarily using chords from other keys. There are four closely related keys in total. Each of them has a reason to be considered closely related to the original key.

Tonic Key

Since “relatedness” is relative, there need to be a reference point, which is called the tonic key. This time, let’s consider C major as the tonic key.

Parallel Key

The term Parallel Key refers to a key with the same tonal center but different major/minor modes. The parallel key to C major is C minor key. In other words, you just need to flip between major/minor to get the parallel key.

To be more precise, when the tonic key is in a major key like this case, the parallel key is minor hence also called Parallel Minor Key. Conversely, when the reference tonic key is in a minor key, the parallel key is called Parallel Major Key.

Relative Key

The term Relative Key refers to a key that share the same scale member (=the same key signature). The relative key to C major is A minor key.
For those who remember the term “relative scale”, which is introduced in the preparation chapter, it’s quite easy to understand. It’s called a relative key because it uses a relative scale.

Dominant Key

Setting the dominant note as the new center results in the Dominant Key.

The “dominant”, do you remember what it is? It was quietly introduced in the Melody Chapter I, which means “the fifth note of the key”. That’s why V is said to have a function called “dominant” and why V₇ is called a “dominant seventh”.

The fifth note in C major key is G, so G major key is the dominant key for C major key.

Subdominant Key

Similarly, The key that sets the subdominant note as the center is called the Subdominant Key. The subdominant is the “fourth note of the key”, so F in C major key. Therefore F major key is the subdominant key for C major key.

2. Circle of Fifths Again

If you want to know these related keys of a certain key, the circle of fifths comes in handy. These related keys are located right next to the tonic key.

Adjacent to the circle of fifths, you’ll find the dominant and subdominant keys, and in the same angular area, you’ll find the relative key.
As a result, a rule emerges: “The dominant key has one more sharp (or one less flat) than the original key,” and “The subdominant key has one more flat (or one less sharp) than the original key”.

Furthermore, the parallel key is obtained simply by switching between major and minor, but if you want to find it on the circle of fifths, it’s located 90 degrees counterclockwise from the original key.

These rules apply no matter where the tonic key is.

Finally, let’s summarize it in a table.

English	Description
Parallel Key	Same tonic, opposite mode (major/minor)
Relative Key	Same key signature, opposite mode (major/minor)
Dominant Key	The dominant note becomes the new center
Subdominant Key	The subdominant note becomes the new center

I’ve introduced the four closely related keys, but this is not knowledge that is frequently required. It’s mostly used in classical music analysis. When you come across terms like these, you can think “Ah, I vaguely remember reading about that,” and refer back to this article, and that should be sufficient.

Summary

• Keys that are in some aspect “related” are termed closely related keys.
• There are four closely related keys: Parallel Key, Relative Key, Dominant Key, and Subdominant Key.

Continue