Keys & Key Signatures

A key defines which group of notes a piece of music uses as its primary tonal material. Being "in the key of C major" means the seven notes of the C major scale are the foundation, and C is the tonal center.

Key Signatures

Rather than writing accidentals on every note, a key signature appears at the beginning of each line of staff notation, telling you which notes are sharp or flat throughout.

Sharp keys (order of sharps: F-C-G-D-A-E-B):

• G major: 1 sharp (F#)
• D major: 2 sharps (F#, C#)
• A major: 3 sharps (F#, C#, G#)
• E major: 4 sharps
• B major: 5 sharps
• F# major: 6 sharps

Flat keys (order of flats: B-E-A-D-G-C-F):

• F major: 1 flat (Bb)
• Bb major: 2 flats (Bb, Eb)
• Eb major: 3 flats (Bb, Eb, Ab)
• Ab major: 4 flats
• Db major: 5 flats
• Gb major: 6 flats

The Circle of Fifths

Arrange all 12 keys around a circle, each a perfect fifth apart clockwise (or a perfect fourth apart counterclockwise). Moving clockwise adds one sharp; moving counterclockwise adds one flat.

This structure reveals deep relationships: keys next to each other share six of seven notes, making modulation between them smooth. Keys opposite each other (e.g., C and F#/Gb) are maximally distant, sharing the fewest notes.

Relative Major and Minor

Every major key has a relative minor that shares the exact same key signature. The relative minor starts on the 6th degree of the major scale. C major and A minor share all the same notes (no sharps or flats). G major and E minor both have one sharp (F#).

Parallel Major and Minor

Parallel keys share the same tonic but different key signatures. C major (no accidentals) and C minor (3 flats) start on the same note but use different collections of pitches. Borrowing chords from the parallel key is a common compositional technique called modal interchange.