From Academic Kids

An accidental is a musical notation symbol used to raise or lower the pitch of a note.


Standard use of accidentals

Accidentals: sharp, flat, natural
Accidentals: sharp, flat, natural

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.

Missing image
Double sharp, double flat

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.

Courtesy accidentals

Although a barline is always understood to cancel the effect of an accidental (except for a tied note), often publishers will use a courtesy accidental as a reminder if the note occurs in the following measure. This usage varies: whereas a few situations are construed to require a courtesy accidental, such as

  • when the first note in a measure is one which had had an accidental applied in the previous measure
  • after a tie carries an accidental across a barline, when the same note appears again in the subsequent measure

other uses are inconsistently applied.

Publishers of jazz music and some atonal music sometimes eschew all courtesy accidentals.

Microtonal notation

Missing image
Quarter-tone accidentals:
half-sharp, sharp, sharp-and-a-half;
half-flat, flat, flat-and-a-half

Composers of microtonal music have developed a number of notations for indicating the various pitches outside of standard notation. One such system for notating quarter tones, used by the Czech Alois Hába and other composers, is shown at right.

In the 19th and beginning 20th century when Turkish musicians switched from their traditional notation systems which were not staff based to the European staff based system, they created a refinement to the European accidental system in order to be able to notate Turkish scales which make use of intervals smaller than the tempered semitone. There are several such systems which vary as to the division of the octave they presupppose or merely the graphical shape of the accidentals. The most widely used system (created by Rauf Yekta Bey) uses a system of 4 sharps (roughly +25 cents, +75 cents, +125 cents and +175 cents) and 4 flats (roughly -25 cents, -75 cents, -125 cents and -175 cents), none of which correspond to the tempered sharp and flat. They presuppose a Pythagorean division of the octave taking the Pythagorean comma (about an 8th of the tempered tone, actually closer to 24 cents, defined as the difference between 7 octaves and 5 just-intonation 5ths) as the basic interval. The Turkish systems have also been adopted by some Arab musicians.

Ben Johnston created a system of notation for pieces in just intonation where the unmarked C, F, and G Major chords are just major chords (4:5:6) and accidentals are used to create just tuning in other keys.

History of accidental notation

All of the symbols are derived from variations of the letter B: the sharp and natural from the square "B quadratum," and the flat from the "B rotundum."

In the beginning of European music notation (4-line staff Gregorian chant manuscripts) only B could be altered (i.e. applied an accidental to: it could be flattened, thus moving from hexachordum durum (i.e. hard hexachord: G-A-B-C-D-E) where it is natural, to hexachordum molle (i.e. soft hexachord: F-G-A-Bb-C-D) where it is flat; B is not present in the third hexachord hexachordum naturale (i.e. natural hexachord: C-D-E-F-G-A)).

This long use of B as the only altered note incidentally helps explain some notational peculiarities: the flat sign actually derives from a round B, to signify the B of the soft hexachord, i.e. B flat (hence the name of the flat sign in French "bémol" from medieval French "bé mol" — modern French "bé mou" — or "soft b") and originally meant only Bb; the natural sign derives from a square B, to signify the B of the hard hexachord, i.e. B natural (hence the name of the natural sign in French "bécarre" from medieval French "bé carre", earlier "bé quarre" — modern French "bé carré" — or "square b") and originally meant only B natural. In the same way, in the German notation the letter B only designates the B flat while the letter H, which is actually a deformation of a square B designates the B natural.

As polyphony became more complex, other notes (than B) needed to be altered in order to avoid undesirable harmonic intervals (especially the augmented 4th that theory writers called "diabolus in musica", i.e. "the devil in music"). The first sharp in use was F#, then came the second flat Eb, then C#, etc.; by the 16th century Bb, Eb, Db, Ab, Gb and F#, C#, G#, D# and A# were all in use.

However, those accidentals were often not notated in vocal scores (but were always notated in tablatures). This notational practice of not marking implied accidentals, leaving them to be supplied by the performer instead, was called musica ficta (i.e. "feigned music").

External Links

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