Music theory definition
Key signature
The sharps or flats at the start of each line, telling you which notes to play sharp or flat throughout.
Keys and signatures
Built on D ? You're in the of D.
Learn it in context
This term is introduced in Unit 6: Keys. Work through the explanations and exercises to connect the definition with music.
- What a key signature tells you
Sharps and flats written once, for the whole piece.
Explore with an interactive tool
- Circle of fifths
Every key, arranged so neighbours share all but one note. Tap a key to turn the circle, see its signature, and hear its chords.
Related music terms
- Key
- The set of notes (and the tonic) a piece is built around, like C major or A minor.
- Circle of fifths
- All twelve keys arranged so each neighbour is a perfect 5th away and differs by one sharp or flat.
- Relative key
- A major and minor key that share a key signature, like C major and A minor.
- Parallel key
- A major and minor key that share a tonic, like C major and C minor.