The key signature in music is represented by one or many flats (b) or sharps (#), so-called accidentals (the exception is C Major for which no accidentals are shown). On music sheets, you will get the statement of the actual key in the notation system at the beginning of a written music piece. You can see symbols for flats or sharps near the clefs, this is the key signature.
Key changes occur in musical pieces, which are indicated by a temporally key signature that turns up in the staff when the change happen.
Examples of key signatures and their symbols
This signifies the key of G. The F position on the musical staff is marked with a sharp symbol and this is because the notes in the G Major key are G, A, B, C, D, E, F#. In musical notation with double note systems (which is the standard form of music written for the piano) the accidentals are placed lower in the bass clef compared to the treble staff. This becomes logical if you are familiar with note reading.
This signifies the key of F. The flat symbol (b) is placed on the B line in the grand staff. The notes in the F Major scale are F, G, A, Bb, C, D, E.
In both cases, the # and b symbols mean that you play on a black key instead of a white. The sharp (#) means that the black key is to the right of the white key and the flat (b) means that the black key is to the left on the white key. F# is, for example, the black key to the right of F and Bb is the black key to the left of B (see also Scale theory – Fundamentals).
Notice that chords aren't affected by key signatures. For example, Bm doesn't become a Bbm in the key of F.
In one case – the key of C (C, D, E, F, G, A, B) – there are neither sharps nor flats indicated:
So what does “in the key of C mean”? It means that the music is played with notes included in the C Major Scale primarily. In these cases, the tune normally starts and, especially, ends on a C note. Although, it is not necessary notes from the C Major Scale throughout the whole tune; other notes can be involved as well as key changes (the key change for a while and when return to the original key).
There are no specific symbols for Minor keys. A key signature doesn't indicate that the piece is played in major, it can also be played in minor. This is because major keys have a relative minor key (learn more about what distinguish keys from scales). If there is a song in A Minor, it is indicated by a C key signature.
List of all keys with accidentals
A complete list of keys with flats and sharps:
C — nor flats or sharps.
G — one sharp.
D — two sharps.
A — three sharps.
E — four sharps.
B — five sharps.
F# — six sharps.
C# — seven sharps.
F — one flat.
Bb — two flats.
Eb — three flats.
Ab — four flats.
Db — five flats.
Gb — six flats.
G# — because of a double sharp it is normally not used.
D# — because of two double sharps it is normally not used.
A# — because of three double sharps it is normally not used.
A good thing to know about is that when keys are indicated, the sharps and flats are always in the same order:
Sharps — F#, C#, G#, D#, A#, E#, B#
Flats — Bb, Eb, Ab, Db, Gb, Cb, Fb
The F sharp key (the picture below) is indicated with six sharps in the following order, from left to right: F#, C#, G#, D#, A#, E#.
Typical keys for the piano and for musical styles
A piano player will by time get familiar with all keys. Nevertheless, some will probably be more frequent in the repertoire. C, F, G, D and Bb are some of the most common keys and are also considered as easier to play compared to keys with more sharps or flats.
Keys such as C, G, D and A are frequent in popular music. In hard rock styles, keys such as E and B are common as well.
The most common keys in jazz are Eb, Bb, F, Ab and Db. Most compositions are written in flatten keys since they are suitable for horns.
If the key doesn't suit the instrument, or the vocal range of the singer, it can be transposed to another key.
See also Famous songs listed by key.