Key signature

:For use in cryptography see Key signature (cryptography)

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In musical notation, a key signature is a series of sharp symbols or flat symbols placed on the staff, designating notes that are to be played one semitone higher or lower unless otherwise noted with an accidental. Key signatures are generally written immediately after the clef at the beginning of a line of musical notation, although they can appear in other parts of a score, usually after a double bar.

Related Topics:
Musical notation - Sharp - Flat - Semitone - Accidental - Clef - Score - Double bar

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Here is a B major scale written with accidentals:

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and here is the same scale (played on the same notes) written using a key signature:

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The effect of a key signature continues throughout a piece or movement, unless explicitly cancelled by another key signature. For example, if a one-sharp key signature is placed at the beginning of a piece, every F in the piece in any octave will be played as F sharp, unless there is an accidental. (If there is only one sharp, it must be F sharp; the sequence of sharps or flats in key signatures is rigid. See below.)

Related Topics:
Octave - Accidental

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In a score containing more than one instrument, all the instruments are usually written with the same key signature. Exceptions:

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• If an instrument is a transposing instrument
• If an instrument is a percussion instrument with indeterminate pitch
• In 15th-century scores partial signatures are quite common, in which different voices will have different key signatures.
 
Key signature: Relation of signature to key ►