A key signature is a set of sharps or flats placed at the beginning of a staff. It tells the performer which notes should be consistently raised or lowered throughout the piece — saving composers from writing an accidental every single time.
What Is a Key Signature?
When a piece of music is in a particular key, certain notes are always sharp or always flat. Rather than marking each one individually, we place all the sharps or flats together at the start of every line. This collection is the key signature.
The Circle of Fifths
The circle of fifths is a visual tool that shows the relationship between all 12 keys. Moving clockwise, each key is a perfect fifth above the previous one and adds one sharp. Moving anticlockwise, each key adds one flat.
Sharp Keys
- G major — 1 sharp (F#)
- D major — 2 sharps (F#, C#)
- A major — 3 sharps (F#, C#, G#)
- E major — 4 sharps (F#, C#, G#, D#)
- B major — 5 sharps (F#, C#, G#, D#, A#)
- F# major — 6 sharps
Flat Keys
- F major — 1 flat (Bb)
- Bb major — 2 flats (Bb, Eb)
- Eb major — 3 flats (Bb, Eb, Ab)
- Ab major — 4 flats (Bb, Eb, Ab, Db)
- Db major — 5 flats (Bb, Eb, Ab, Db, Gb)
- Gb major — 6 flats
Relative Minor Keys
Every major key has a relative minor that shares the same key signature. The relative minor is always found a minor third (3 semitones) below the major key. For example, A minor is the relative minor of C major — both have no sharps or flats.