Key Signatures: Up to One Sharp or Flat
The sharps or flats written at the start of a stave that belong to the whole piece — starting with keys that have just one.
Explainer
A key signature is a set of sharps or flats written right after the clef, telling you which notes are consistently raised or lowered throughout the piece.
C major has no sharps or flats — just the plain white notes.
G major has one sharp: F♯. Every F in the piece is played as F♯ unless marked otherwise.
F major has one flat: B♭. Every B in the piece is played as B♭.
Worked examples
Example 1
C major — no sharps or flats
The simplest key of all — just the white notes, C to C.
Example 2
G major — one sharp (F♯)
Every F becomes F♯.
Example 3
F major — one flat (B♭)
Every B becomes B♭.