Accidental (music)
In musical notation, an accidental is a symbol that changes the current pitch of a space or line on a staff. Accidentals are used both to specify a key signature and to change individual notes throughout the course of a piece. The rather presumptuous term accidental possibly refers to the older sense of accidental meaning outside the norm, as accidentals are used to indicate a pitch that is off-key.
Reading Accidentals
An accidental can be a sharp, a flat, a natural, a double-sharp, or a double-flat. Once a particular line or space is given an accidental, that line or space carries that new meaning to the end of the measure. At the beginning of the next measure, all lines and spaces "reset" to the last key signature value.
All accidentals, regardless of the current key, modify their following notes as if they began in the key of C, as follows:
- A sharp raises the pitch by one semitone, or minor second.
- A double-sharp raises the pitch by two semitones, or one major second.
- A flat lowers the pitch by one semitone.
- A double-flat lowers the pitch by two semitones.
- A natural defeats any previous sharp or flat (including in the key signature). Any note following a natural mark will be part of the key of C major.
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Top staff, left to right: a B-flat, on key; a B-natural, the same B that is in the key of C; a B-double-flat, two semitones below B (also known as A); an F-double-sharp, two semitones above F; an F-natural, defeating the double-sharp; another F-natural, without the need for a second accidental; an F-sharp, one semitone above F; and another F-sharp. Bottom staff: The exact same pitches, technically called enharmonic spellings, written in the key of C. |
Writing Accidentals
When an accidental note is tied across a barline, no additional accidental is needed, as it is implied by holding the note.
Although a barline implicitly resets all lines and spaces to the last key signature, typically a courtesy accidental will be placed before any on-key note that was modified in the previous measure, spelling the on-key note explicitly. This is done to help with sight reading.
The general rules for choosing between flat or sharp accidentals are:
- When descending, use flats.
- When ascending, use sharps.
- Try to use the same kind of accidentals--sharps or flats--used by the key signature.
- Ignore the above rules if a more familiar notation appears (e.g., choose F-sharp over G-flat when showing a D major chord, even if you are descending in the key of E-flat).
- Never use double-flats or double-sharps unless there is no other option.
- See also music basic topics