Accidental (music) - Standard Use of Accidentals

Standard Use of Accidentals

In most cases, a sharp raises the pitch of a note one semitone while a flat lowers it a semitone. A natural is used to cancel the effect of a flat or sharp. This system of accidentals operates in conjunction with the key signature, whose effect continues throughout an entire piece, unless canceled by another key signature. An accidental can also be used to cancel or reinstate the flats or sharps of the key signature.

Since about 1700, accidentals have been understood to continue for the remainder of the measure in which they occur, so that a subsequent note on the same staff position is still affected by that accidental, unless marked as an accidental on its own. Notes on other staff positions, including those an octave away, are unaffected. Once a barline is passed, the effect of the accidental ends, except when a note affected by an accidental is tied to the same note across a barline. In this case subsequent notes at the same staff position in the second bar are not affected by the accidental carried through with the tied note. Sight reading music at speed can be mentally (and physically) taxing, so where an editor or engraver sees a possible opportunity for confusion, a courtesy or cautionary accidental may be placed by a note whose pitch is, strictly speaking, already given by the key signature. This accidental is usually within parentheses.

Though this tradition is still in use particularly in tonal music, it may be cumbersome in music that features frequent accidentals, as is often the case in non-tonal music. As a result, an alternate system of note-for-note accidentals has been adopted with the aim of reducing the number of accidentals required to notate a measure. The system is as follows:

1. An accidental carries through the measure affecting both the note it immediately precedes and any following notes on the same line or space in the measure.
2. Accidentals do not affect the same note of a different octave, unless indicated by a key signature.
3. Accidentals are not repeated on tied notes unless the tie goes from line to line or page to page.
4. Accidentals are not repeated for repeated notes unless one or more different pitches intervene.
5. If a sharp or flat pitch is followed directly by its natural form, a natural is used.
6. Cautionary accidentals or naturals (in parentheses) may be used to clarify ambiguities, but should be held to a minimum.

Because seven of the twelve notes of the chromatic equal-tempered scale are naturals, (the "white notes" A,B,C,D,E,F and G on a piano keyboard), this system can significantly reduce the number of naturals required in a notated passage.

Note that in a few cases the accidental might change the note by more than a semitone: for example, if a G sharp is followed in the same measure by a G flat, the flat sign on the latter note means it will be two semitones lower than if no accidental were present. Thus, the effect of the accidental has to be understood in relation to the "natural" meaning of the note's staff position. For the sake of clarity, some composers put a natural in front of the accidental. Thus, if in this example the composer actually wanted the note a semitone lower than G-natural, he might put first a natural sign to cancel the previous G-sharp, then the flat. However, under most contexts, an F-sharp could be used instead.

Double accidentals raise or lower the pitch of a note by two semitones, an innovation developed as early as 1615. This applies to the written note, ignoring key signature. An F with a double sharp applied raises it a whole step so it is enharmonically equivalent to a G. Usage varies on how to notate the situation in which a note with a double sharp is followed in the same measure by a note with a single sharp: some publications simply use the single accidental for the latter note, whereas others use a combination of a natural and a sharp, with the natural being understood to apply to only the second sharp.

The double accidental with respect to a specific key signature, raises or lowers the notes containing a sharp or flat by a half step. For example, when in the key of C-sharp minor or E major, F,C,G, and D contain a sharp; adding a double accidental (double sharp) to F for example in this case would only raise the already sharp containing note F one half step or semitone, creating G natural, respectively. Conversely, if a double sharp were added to any other note not containing a sharp or flat as indicated by the key signature then the note will be raised two semitones or a whole step with respect to the chromatic scale. For example, in the aforementioned key signature any note that is not F, C, G, and D will be raised by a whole step or two semitones instead of one, so an A double sharp raises the note A to the enharmonic equivalent of B.