Key Signatures

A key signature is a symbol used in music notation telling you what key a song or piece of music is in. We haven’t started talking about keys just yet. There is a lot to discuss about keys and we will do that in later lessons. This lesson is just to explain key signatures used in written music. But, I’ll give you a little preview about keys so you can better understand key signatures.

What is a Key?

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

Every key has a unique set of seven notes. For example, the key of C Major uses the notes C, D, E, F, G, A, and B. The key of C Major contains no sharps or flats. It is the only major key with no sharps or flats.

As another example, the key of D Major uses the notes D, E, F♯, G, A, B, and C♯. The key of D Major has two sharps — F♯ and C♯. Again, D is the only major key with two sharps.

As a third example, the key of E♭ Major uses the notes E♭, F, G, A♭, B♭, C, and D. E♭ Major has 3 flats — B♭, E♭, and A♭, and it’s the only major key with 3 flats.

Keys will have either sharps or flats, never a mix of the two.

The main point is: each key has its own unique set of notes and a unique number of sharps or flats. Those unique notes define the key.

What is a Key Signature?

The key signature is a group of sharps or a group of flats written at the beginning of the music. The key signature's sharps or flats tells you which notes are sharp or flat throughout the music. Since each key has a unique number of sharps or flats, the number of sharps or flats in the key signature tells you what key the music is in. The key signature is written on the staff after the clef symbol.

There are 12 possible keys and 15 different key signatures for identifying them. At this point in the lessons don't worry about memorizing the key signatures just yet. We will cover them in more detail later.

Using our key examples above, the key of D would show 2 sharps as its key signature. If you see a key signature of 2 sharps, you know it is the key of D because the major key of D is the only key with 2 sharps. Specifically, those two sharps are F♯ and C♯, and the sharps are written on the F line and C space of the bass clef staff.

The key of E♭ would show 3 flats as its key signature. E♭ major is the only major key with 3 flats (B♭, E♭, and A♭).

The key of C would show nothing since it has no sharps or flats.

With time and practice you will memorize all 15 key signatures. This will go hand in hand with learning scales and harmony.

How Do Key Signatures Work in Written Notation?

In music notation, the key signature tells the reader which notes to play sharp or flat throughout the music. If you are playing a song in a certain key, the same notes will be sharp or flat throughout the entire song. Instead of writing sharps or flats for each note every time it occurs in the music, the sharps or flats of the key are placed at the beginning of the music in the key signature. The reader is expected to remember to sharp or flat those notes as they play. This may sound like a lot of mental work, but the more you know and understand your keys, it makes things much simpler.

In the following example, you can see the notes of the D Major scale written without a key signature. Next to it are the very same notes using the key signature for D Major — 2 sharps. Notice, with the addition of the key signature, F♯ and C♯ no longer need a ♯ written before them. F and C are always sharp unless noted otherwise using a natural symbol (♮). All key signatures work this same way.

Notice that the sharps and flats apply, not only to the line or space on which they are written, but to all instances of that note in the music. For example, F♯ is written on the 4th line from the bottom, but any F anywhere on the staff is to be played as F♯--not just that 4th line F.

The Order of Sharps and the Order of Flats

The sharps and flats of the key signature always follow a specific order and are always written in that order. There is a logic for this order, but we will look at this later.

The order of flats is: B♭, E♭, A♭, D♭, G♭, C♭, F♭

The order of sharps is: F♯, C♯, G♯, D♯, A♯, E♯, B♯

You might notice they are the same order of notes only reversed. When we discuss keys and harmony I will explain why you want to memorize these orders of flats and sharps. For now, it's enough that you know there is a specific order in which the flats and sharps are always written.

Key Signature Summary

This key signature system may seem like more work than less, but it’s not. As you begin to memorize keys like every musician should, you will see it makes more sense this way and written music is neater and easier to read. Once again, reading music will force you to learn the basics of music just a little bit better.