The Key Signature

We use scales as the building blocks for much of the music we hear. In classical music, when a piece is based on a particular scale it is often mentioned in the title, but instead of using the word scale, we use the word key. For example, let's say a symphony is written using mostly the notes of the C major scale. The title might be something like, "Starlight Symphony in the Key of C Major." The term key here means that a piece of music revolves around a central pitch, and often this includes whether the scale based on that pitch will be major or minor. For example, a song in the key of G minor tells the listener that the central pitch in the song is G and the G scale used is minor.

Writing pieces in different keys allows for subtle shifts in the emotion and color. Consequently pieces of music are written in a great variety of keys. Sometimes a particular key is also used for practical reasons, such as to better suit a specific vocal type, or a specific instrument. For instance, string instruments like the violin and cello tend to work best using keys with sharps in them, whereas woodwinds tend towards keys with flats. We know from our exercises that some scales contain a LOT of accidentals, so the common notation system has a very efficient way of telling musicians which notes will need accidentals: the key signature.

The key signature is a collection of all the accidentals present in a particular scale. So let's begin by looking at a piece of music written in the key of A-flat major (remember, this means the notes used in the piece are the notes that belong in the A-flat major scale). When a piece of music is written in this fashion, the music must reflect the specific notes of the A-flat major scale: A-flat, B-flat, C, D-flat, E-flat, F, and G. This means that every A, B, D, and E note in the piece needs to have a flat, as in the example below.

Example Without a Key Signature

The number of flats showing in the example above is a bit repetitive, as the musician will likely notice that the same four notes are being flatted throughout the piece. It is also very busy to the eye (and a waste of ink!) to see all these accidentals. The solution is to place a key signature at the beginning of the piece that tells the musician which notes are flatted or sharped across the entire piece. The four flats are present at the beginning of each line of music just to the right of each clef. In this case, because the scale of A-flat has four flats, the flats in the signature lie exactly on the lines for B and D and the spaces for E and A. This tells the musician that every B, E, A, or D in the piece is flat, then the player simply has to remember to play those four notes flat when she sees one. With the key signature we have a much more efficient way to write down the piece of music, the two examples sound identical, and the score looks much cleaner to the eye.

The key signature always appears just to the right of the clef on the staff, and these are placed on every musical staff in a given piece of music. The C major scale has no sharps or flats, so no key signature means the C scale is likely being used. All other scales will have one or more sharps or flats. Keys that contain sharps are typically referred to as "sharp keys" and keys that contain flats are referred to as "flat keys." When we notate a key signature, we write each sharp or flat in a very specific order and in a specific place for each clef. The maximum number of flats or sharps in any scale is seven (this covers all seven letters of the musical alphabet). To be able to notate key signatures, you should practice writing the sets of all seven sharps and all seven flats that you see below on your own manuscript paper. Pay special attention to where each accidental lies in relation to the clef and staff lines.

Key Signature showing all Sharps

Key Signature showing all Flats

Key signature accidentals are always written in a specific order. For example in keys with sharps, F-sharp is always written first (at the far left), then C-sharp, then G-sharp. In keys with flats, B-flat is always written first, then E-flat, then A-flat, etc. It is important to memorize this special order for both sharps and flats, which are referred to respectively as the Order of Sharps and the Order of Flats. You will notice that the example key signatures above follow these orders exactly.

  • The Order of Sharps: F-C-G-D-A-E-B
  • The Order of Flats: B-E-A-D-G-C-F

No matter what scale we write, the key signature always summarizes the accidentals it contains using these special patterns. So even though the A-flat major scale is notated in alphabetical order: A-flat, B-flat, C, D-flat, E-flat, F, G, A-flat. Its key signature (see example) will be written using the Order of Flats: B-flat, E-flat, A-flat, D-flat.

A-flat Major

Since it is important to memorize the two orders of accidentals, there are a few mnemonic devices you might use. You only need to remember one, as once you have one order, the other will be its reverse. One nice one for the Order of Sharps is: "Father Charles Goes Down And Ends Battle." Then to find the order of flats just reverse it. The popular mnemonic for the Order of Flats is "BEAD Greatest Common Factor," then reverse the order of flats to find the sharp order. Again, we suggest you just memorize whichever of these you like more, then reverse it to find the remaining set.

Identifying Major Key Signatures

To name key signatures, we simply give the letter name of the scale associated with the sharps or flats shown. For example, if given a key signature with one sharp, we would need to find the major scale that has one sharp, which is G major, then we would simply name the key signature by saying the piece is in the "key of G major."

Key signatures apply to both major and minor scales, but we will focus on naming major key signatures here and minor key signatures once we have learned to build minor scales. There are a couple methods for quickly recognizing key signatures. As we learned previously, the key signature for the C scale has no sharps or flats, so you should just memorize that no key signature means the key of C major. For key signatures that contain sharps, the scale will always be a diatonic half step above the last sharp (the farthest sharp to the right). For example, if your key signature has two sharps, they will be F-sharp and C-sharp. The last sharp is C-sharp, a diatonic half step above is D, so a key signature with two sharps is the key of D major. For key signatures that contain flats, we name the second-to-last flat (the second flat from the right). For example, if your key signature has two flats, they will be B-flat and E-flat. The second-to-last flat is B-flat, therefore we have the key of B-flat. There is one caveat for this rule, since we need at least two flats to have a second-to-last, we also have to memorize the key that has only one flat, which is F major. To summarize:

  • The key signature with no sharps or flats: C major
  • Keys with sharps: go up a diatonic half step from the last sharp
  • Keys with flats: name the second-to-last flat
  • The key signature with one flat: F major

Here are a few examples. Click the button to see a key signature, click the button below to see its name. *Keep an eye on the clef!

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