Accidental music: Encyclopedia II - Accidental music - Standard use of accidentals

Accidental music - 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.

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 replaced by an accidental of 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 (either explicit or implied from earlier in the measure) is tied to the same note across a barline; see courtesy accidentals, below.

This use contrasts with the key signature, whose effect continues throughout an entire piece, unless cancelled by another key signature. An accidental can be used to cancel or reinstate the flats or sharps of the key signature as well for the duration of a measure.

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.

Double accidentals raise or lower the pitch of a note by two semitones, an innovation developed as early as 1615. An F with a double sharp applied raises it a whole step so it is enharmonic with 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 the second sharp only.

Adapted from the Wikipedia article "Standard use of accidentals", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki