In music, a key signature is a symbol that usually appears on sheet music to tell you what key a piece of a song is in. Most major and minor keys include accidental notes such as a sharp (♯), a flat (♭) or sometimes a natural (♮), however, in signature keys these notes are rearranged to the beginning of the staff to make it easier to read.
This form of music notation was not common until the late Baroque and early Classical period. However, some music that was composed between the 1720s -1740s used key signatures showing accidentals on both octaves for notes which fall within the staff.
Either made up of a group of flats or a group of sharps, a key signature appears written on the staff and will fall in between the clef symbol and the time signature.
There are 15 different key signatures to identify 12 different notes. The key signature is a sign to the musician that they need to change the way the note is played so it fits with the key.
The key of C Major uses the notes C, D, E, F, G, A, and B. The key of C Major uses no sharps or flats. It is the only major key using no sharps or flats so therefore the signature key remains blank.
To illustrate key signatures a bit better we are going to use D Major. The major scale 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#. This scale is the only major key with two sharps.
From above, you can see the key signature is just a grouping of the accidentals that would have appeared in the scale. It makes music much simpler to read and allows the musician to identify the “key” of the music more easily.
In music notation, the key signature tells the musician which notes to play sharp or flat. If you are playing a song in a certain key, the same notes will be sharp or flat during the entire song. The same notes appear numerous times throughout songs – having to write flats major or sharps every time a certain note appears can be a tedious process.
Instead, a key is placed at the beginning of the music in the key signature. The reader is expected to remember to sharp or flat those notes as he or she plays.
Below is a table that is referenced from musicnotes website (thank you) which illustrates the relationship of the 12 different notes and their relative key signatures.
There is a certain order that a note or pitch that is not a part of the scale is written in a key signature. If you have studied the circle of fifths than this will not be news to you. If you are unaware of the pattern, there are two easy rhymes to help you remember:
Below are the keys in order of how many sharps/flats there are in each key:
You should always keep in mind that for every major key signature there is a relative minor.
It is vital that musicians memorise all the key signatures, including both variations of the Enharmonic keys. Enharmonic Keys are key signatures that have the same pitches but are named differently.
These keys are B Major/Cb Major, F# Major/Gb Major, and C# Major/Db Major.
These three sharp/flat keys are practically the same on the piano or keyboard and share the same place on the Circle of Fifths, but they can be identified with two different names and function differently in music theory. You should also remember there is a natural key.
As mentioned above, the key of C major has no accidental keys and therefore is a neutral signature key.
This key signature system may seem like a lot to remember, but in theory, it is quite simple to grasp.
As you begin to memorise keys as every musician should, you will see it is more practical for the notes to be written this way as it makes music a lot easier to read.
Knowing key signatures when it comes to playing your instrument will enhance your ability to play and write more freely and be more creative with music composition.
Getting to grips with the way the music is written will also allow you to develop a better understanding and knowledge of the fundamentals of music.
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