What are Key Signatures and How Do You Write Them?

So as the key signature has these two sharps, this piece is in D Major. D major has two sharps and is the only major scale to have this specific key signature. For more on why this key is called D Major, check out our Major Keys post.

A great way to remember the names and see the relationships between all the key signatures is to understand the circle of fifths. This diagram supports our understanding of key signatures and deserves its own post as it is so important!

Once you have a good understanding of the different scales/keys it is then important to look at how to write these sharps and flats into the key signature. 

There is a specific order to how the sharps and flats are written in key signatures.

The order of the sharps is as follows -F# C# G# D# A# E# B#.

It is much easier to remember the order of these sharps with a mnemonic to begin with. You can make your own up, but my favourite is Father Christmas Gets Dad An Electric Blanket.

The order of the flats is - Bb Eb Ab Db Gb Cb Fb.

Again, it is much easier to remember the order of these flats with a mnemonic. You can make up your own but my favourite for this one is: Blanket Explodes And Dad Gets Cold Feet.

Note that a key signature will only be written in all sharps or all flats, there will never be a mixture. 

Below you can see tables of our sharp and flat key signatures. 

The key signatures will only tell you the Major key that the piece is in and not their relative minor. By memorising the circle of fifths you can know the relative minor to each major key. This will help to work out if the piece is written in the major scale or the relative minor scale.

Both of the major and its relative minor scales share the same key signature and therefore it is important to look out for extra accidentals (sharps or flats) in the piece, in addition to those in the key signature. If there are any extra accidentals this may mean that the piece is written in a minor key. See our Minor Scales post for more info.

Key signatures can be written in all four of the main clefs. For the treble, bass and alto clef, the order and position of the accidentals on the stave does not change. They follow the pattern of first sharp high on the stave, the second sharp low, third sharp high etc. The flat key signature starts with the first flat low on the stave, then we move up for the next one, back down, etc. The tenor clef is slightly different. The flat keys follow the same pattern but for the sharp keys, the pattern is the opposite to the other clefs. The first sharp starts low on the stave, then we move up for the next one, back down etc. Take a look at the diagram below.

The short answer is, yes you can! Many songs and pieces of music change key signatures part way through and this will be shown with a new key signature written part way through the music.

The piece above begins in the key of G major and then changes to the key of D major. This is called a key change or a modulation.

We usually modulate to a relative key! To find out more check out the post on modulating!

Many pop songs also have key changes and there are a few examples below: