Key Signatures

David Loberg Code, Western Michigan University

Keys come from scales.  People sometimes make the mistake of thinking that keys come from key signatures.  They might say that A major has 3 sharps because of the key signature.  This is backwards.  It is like saying that deer like to cross the road at particular spot because there is a Deer X-ing sign there.  Key signatures are signs.  They help remind us of the key and save us the trouble of writing the same sharps or flats over and over again.  The easiest and best way to determine a key signature is to think of the scale.  When you play a D major scale, you use an F# and a C#, therefore the key signature for D major has 2 sharps (F# and C#).  For uniformity, the sharps or flats in a key signature are always written in the same order (regardless of what order they appear in the scale.)

For example, an A major scale is: A B C# D E F# G# A.  In the key signature, however, the order of the sharps is rearranged: F#, C#, G#.

The order of sharps is always as follows:

F#              C#              G#             D#            A#              E#              B#

Fat             Cats            Go              Down       Alleys             Eating         Birds

Father              Charles               Goes                    Down           And                        Ends                 Battle

The order of flats is coincidentally the same sequence but backwards:

Bb              Eb              Ab              Db              Gb              Cb              Fb

Big              Elephants   Always        Do              Great          Circus         Feats

Battle                  Ends                And                 Down                  Goes                 Charles'             Father

There are other tricks you can use to determine the name of the key from looking at the key signature.  For Major keys, the last sharp in the key signature is always Ti (the seventh scale degree).  To find the key, simply go up a minor second (to Do).  For example:

The key signature has 5 sharps (F#-C#-G#-D#-A#).

The last sharp will be A# (Alleys)

A minor 2nd (half step) above A# is B.

The major key is B major.

For Major key signatures with flats, the second to last flat is always Do.

The key signature has 4 flats (Bb-Eb-Ab-Db).

The second to last flat is Ab.

The major key is Ab major.

Obviously, these tricks will not work for C major (no sharps or flats), or F major (1 flat).  You will just need to memorize these.  Also, these tricks do not work for minor keys.