Key Signatures

A key signature is a sign written at the beginning of each line of music which indicates the frequent use of accidentals, thus dispencing the need to write them throughout a piece.

Figure 1: A key signature after a treble clef.

The Circle of Fifths

A way of identifying key signatures and which accidentals belong to each key is to study the circle of fifths:

Figure 2: The glorious circle of fifths!

To identify how many sharps or flats belong to each key, simply count left or right from C:

Left: C = 0 flats, F = 1 flats, Bb = 2 flats, Eb = 3 flats, etc.

Right: C = 0 sharps, G = 1 sharps, D = 2 sharps, A = 3 sharps, etc.

To identify which sharps or flats belong to each key, count left or right from in-between Bb and F:

- For sharps you count right (F, C, G, D, A, E, B). A good mnemonic for remembering this order of sharps is Fat Cats Go Down Alleys Eating Birds.

- For flats you count left (B, E, A, D, G, C, F). A good mnemonic for remembering this order of flats is Battle Ends And Down Goes Charles' Father.

It should be noted that every major key has a relative minor key and vice versa. This is because they share the same set of diatonic notes, but each has a different tonic. The following table shows a list of relating keys:

Major Key Minor Key
C Major A Minor
G Major E Minor
D Major B Minor
A Major Gb Minor
E Major Db Minor
B Major Ab Minor
Gb Major Eb Minor
Db Major Bb Minor
Ab Major F Minor
Eb Major C Minor
Bb Major G Minor
F Major D Minor

Another way to recognize a relative key from major to minor is to simply count a minor third descending; and from minor to major, a minor third ascending:

Figure 3: Counting a min. 3rd between two tonic chords.

There is no way to emphasize how important the cycle of fifths is and should be well studied until memorized.

Figure 4: A diagram of all key signatures.

Also see Accidentals | Lyrics.

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