Natural (music)
In modern Western music notation, a natural is a symbol that cancels a previous sharp or flat in the written music. It indicates that the note is at its unaltered pitch.
The natural symbol can be used as an accidental to cancel sharps or flats on an individual note. It may also be shown in a key signature to indicate that sharps or flats in a previous key signature are cancelled. A note is referred to as 'natural' when the letter-name note is not modified by a flat or sharp. These notes correspond to the white keys on the keyboard of a piano.
The natural sign is derived from a square b used to denote B in medieval music.
Usage
Like all accidental markings, the natural symbol is written to the left of the note head and applies to subsequent notes of the same pitch through the remainder of the measure.A note marked with a natural sign can be changed to a flat or sharp by simply applying the new accidental.
A natural sign cancels a flat or sharp from a previous note or key signature.
Sometimes these cancelling naturals at a key change are omitted, but they must be used if the new key has no sharps or flats.
Double natural
A double natural is a symbol that has two naturals. It may be used to cancel a double flat or double sharp, but in modern notation a single natural sign is acceptable.Similarly, a double flat or double sharp can be changed to a single flat or sharp with a simple ♭ or ♯, but older notation may use ♮♭, ♭♮, ♮♯ or ♯♮ instead. Triple sharps and triple flats are extremely rare, but may be canceled using the same notation options. When changing a flat to a sharp or vice-versa, the combined symbols ♮♯ or ♮♭ can be used.