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What Is a Key in Music? A Comprehensive Guide

August 4, 2023
what is a key in music

Don’t fret – you know exactly what a key is.

If you know the alphabet, then you know keys.

C-minor, A, G – sound familiar? Good. But let’s dig into musical keys a bit further.

We all need some hand-holding now and again, and that’s what we are here for. 

Get ready to learn ‘what is a key in music’.

What the Key?

Unlike a key that opens a door, a key in music is the main group of pitches or musical notes that form the harmonic foundation of a musical composition.

A key is the major or minor scale around which a piece of music revolves.

A song in a major key is based on a major scale.

A song in a minor key is based on a minor scale.

The pitches in a song are usually from one particular scale, and we typically use the key of the first note to name the scale. 

The first key in a scale is known as the tonic and is the foundation, or tonal center, of the song.

A tonic exerts something of a sonic gravitational pull on a piece of music.

It is the stable core of the song and every other note in the key will possess a natural-sounding relationship with it.

Some people consider the tonic the home base of the key, and whenever you return to it you feel like you are returning home, and in the sense that the progression sounds complete and satisfying.

As a beginner, you’ll typically learn the C-major key or the A-minor key, for instance. C-major and A-minor are the tonics of each respective key.

What are the Keys?

Before you panic and start breaking out the flashcards, you’ll be happy to know that there are only 12 major keys and 12 minor keys for the two main types of music scales.

Major keys are based on a major scale, and minor keys are based on a minor scale.

Here they are in all their glory:  

A, A#, B♭, B, C, C#, D♭, D, D#, E♭, E, F, F#. G♭, G, and G#, A♭. 

Any of these notes can be the tonal center, or tonic, of the song.

A piece of music can use all the notes in the key or just a selection of notes from the key.

You can incorporate notes from other keys into the song but this is less common and can create a discordant, unappealing sonic effect.

What are Sharps & Flats?

But wait.

What is ♭?

What is #?

What is the difference between D-sharp and G-flat?

Don’t let the musical terminology get you down – it can be confusing for anyone at first glance.

You’ll often hear the words sharp and flat get bandied around in music theory so it is imperative to understand what they mean.

In the simplest terms, sharp notes raise a pitch while flat tones lower a pitch.

They both modify the natural notes and give them a distinct character.

Sharp notes sound a semitone higher than the natural version of the note indicated on the staff.

Flat notes sound a semitone lower than the natural version of the note indicated on the staff.

C-major and A-minor scales contain neither sharp nor flat keys.

On a piano keyboard, all of the black keys can be notated as “flats” and/or “sharps.”

Relative Keys

A major key and a minor key are relative when they share all of the same notes.

For example, the keys of G-major and E-minor are relative to each other: C-major and A-minor are relative keys.

Each major key has a relative minor key and vice versa.

The root note of the relative minor key is a minor third below the root note of the major key. 

This is a visual table of the relative keys.

Relative keys visual table

Parallel Keys

Major and minor keys are considered parallel to each other when they share the same root note.

The keys of C-major and C-minor are parallel, for instance.

Parallel keys have different notes, however, which is how they differ from relative keys. 

It is vital to note that minor keys differ from major keys in that the third, sixth, and seventh degrees in the key are lowered by a half step.

Which makes sense when you read up on the differences between the minor scale and the major scale.

What is a Key Signature?

See that little symbol right after the clef sign and right before the time signature?

That is the key signature.

The key signature provides insight into what key a given piece of music is written in and communicates to the musician what flats or sharps will appear in the song.

Quick recap.

There are 15 major scales that correspond with 15 key signatures.

There are seven keys with sharps and seven with flats, and one, C major, that does not have any sharps or flats.

There are always two keys that share the same key signature.

There is always a major and minor key for each key signature.

For the sharp keys, the first key in every key signature is always F-sharp, followed by C-sharp, G-sharp, D-sharp, A-sharp, E-sharp, and B-sharp.

That means if you see two sharp symbols, you will play F-sharp and C-sharp.

If you see one, you will only play F-sharp.

In every flat key signature, the first flat is always B-flat, followed by E-flat, A-flat, D-flat, G-flat, C-flat, and F-flat.

If you see one flat symbol, for instance, you will play B-flat.

Music students often refer back to the circle of fifths, a diagram that aids in memorizing and understanding the 24 major and minor keys.

Whenever the root note is raised by a perfect fifth from C-major, a sharp is added to the key.

For example, the key of G-major (a perfect fifth above C-major) has one sharp.

If you remember the major keys, you can also use the diagram to find the relative minor keys.



If you’re in a major key, you will move down three semitones to find the relative minor.

If you’re in a minor key, you will move up three semitones to find the relative major.

Relative keys Diagram for Major and Minor Keys

Hurry, the Door is Open  

Sometimes all you need is the right key for the right door.

When it comes to music theory, consider keys your entry point to a wonderful world of sound, composition, and creative collaboration. 

Once you have memorized the keys, you will open up a whole new “room” of possibilities, and you will have an academic – and acoustic – understanding of how to play and produce compelling, attention-commanding songs.

You may also like: What Is an Interval in Music?

Will Fenton

Will, the founder of MIDDER, is a multifaceted individual with a deep passion for music and personal finance. As a self-proclaimed music and personal finance geek, he has a keen eye for futuristic technologies, especially those that empower creators and the public.

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