In music

Music

Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...

, an accidental is a note

Note

In music, the term note has two primary meanings:#A sign used in musical notation to represent the relative duration and pitch of a sound;#A pitched sound itself....

 whose pitch

Pitch (music)

Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...

 (or pitch class

Pitch class

In music, a pitch class is a set of all pitches that are a whole number of octaves apart, e.g., the pitch class C consists of the Cs in all octaves...

) is not a member of a scale

Musical scale

In music, a scale is a sequence of musical notes in ascending and descending order. Most commonly, especially in the context of the common practice period, the notes of a scale will belong to a single key, thus providing material for or being used to conveniently represent part or all of a musical...

 or mode

Musical mode

In the theory of Western music since the ninth century, mode generally refers to a type of scale. This usage, still the most common in recent years, reflects a tradition dating to the middle ages, itself inspired by the theory of ancient Greek music.The word encompasses several additional...

 indicated by the most recently applied

Modulation (music)

In music, modulation is most commonly the act or process of changing from one key to another. This may or may not be accompanied by a change in key signature. Modulations articulate or create the structure or form of many pieces, as well as add interest...

 key signature

Key signature

In musical notation, a key signature is a series of sharp or flat symbols placed on the staff, designating notes that are to be consistently played one semitone higher or lower than the equivalent natural notes unless otherwise altered with an accidental...

. In musical notation

Musical notation

Music notation or musical notation is any system that represents aurally perceived music, through the use of written symbols.-History:...

, the symbols used to mark such notes, sharps

Sharp (music)

In music, sharp, dièse , or diesis means higher in pitch and the sharp symbol raises a note by a half tone. Intonation may be flat, sharp, or both, successively or simultaneously...

 , flats , and naturals , may also be called accidentals. An accidental sign raises or lowers the following note from its normal pitch, usually by a semitone

Semitone

A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically....

, although microtonal music

Microtonal music

Microtonal music is music using microtones—intervals of less than an equally spaced semitone. Microtonal music can also refer to music which uses intervals not found in the Western system of 12 equal intervals to the octave.-Terminology:...

 may use "fractional" accidental signs, and one occasionally sees double sharps or flats, which raise or lower the indicated note by a whole tone

Major second

In Western music theory, a major second is a musical interval spanning two semitones, and encompassing two adjacent staff positions . For example, the interval from C to D is a major second, as the note D lies two semitones above C, and the two notes are notated on adjacent staff postions...

. Accidentals apply within the measure

Bar (music)

In musical notation, a bar is a segment of time defined by a given number of beats of a given duration. Typically, a piece consists of several bars of the same length, and in modern musical notation the number of beats in each bar is specified at the beginning of the score by the top number of a...

 and octave

Octave

In music, an octave is the interval between one musical pitch and another with half or double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems"...

 in which they appear, unless canceled by another accidental sign, or tied

Tie (music)

In music notation, a tie is a curved line connecting the heads of two notes of the same pitch, indicating that they are to be played as a single note with a duration equal to the sum of the individual notes' note values...

 into a following measure.
The modern accidental signs derive from the round and square small letter b

B

B is the second letter in the basic modern Latin alphabet. It is used to represent a variety of bilabial sounds , most commonly a voiced bilabial plosive.-History:...

used in Gregorian chant

Gregorian chant

Gregorian chant is the central tradition of Western plainchant, a form of monophonic liturgical music within Western Christianity that accompanied the celebration of Mass and other ritual services...

 manuscripts to signify the two pitches of B, the only note that could be altered. The round b became the flat sign, while the square b diverged into the sharp and natural signs.

Sometimes the black keys on a musical keyboard

Musical keyboard

A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument, particularly the piano. Keyboards typically contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the...

 are called accidentals or sharps, and the white keys are called naturals.

Standard use of accidentals

In most cases, a sharp

Sharp (music)

In music, sharp, dièse , or diesis means higher in pitch and the sharp symbol raises a note by a half tone. Intonation may be flat, sharp, or both, successively or simultaneously...

 raises the pitch of a note one semitone

Semitone

A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically....

 while a flat lowers it a semitone

Semitone

A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically....

. A natural is used to cancel the effect of a flat or sharp. This system of accidentals operates in conjunction with the key signature

Key signature

In musical notation, a key signature is a series of sharp or flat symbols placed on the staff, designating notes that are to be consistently played one semitone higher or lower than the equivalent natural notes unless otherwise altered with an accidental...

, 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

Bar (music)

In musical notation, a bar is a segment of time defined by a given number of beats of a given duration. Typically, a piece consists of several bars of the same length, and in modern musical notation the number of beats in each bar is specified at the beginning of the score by the top number of a...

 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

Octave

In music, an octave is the interval between one musical pitch and another with half or double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems"...

 away, are unaffected. Once a barline is passed, the effect of the accidental ends, except when a note affected by an accidental is tied

Tie (music)

In music notation, a tie is a curved line connecting the heads of two notes of the same pitch, indicating that they are to be played as a single note with a duration equal to the sum of the individual notes' note values...

 to the same note across a barline. Sight reading

Sight reading

Sight-reading is the reading and performing of a piece of written music, specifically when the performer has not seen it before. Sight-singing is often used to describe a singer who is sight-reading.-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 [or rests] 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

Semitone

A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically....

: 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 . An F with a double sharp applied raises it a whole step so it is enharmonic

Enharmonic

In modern musical notation and tuning, an enharmonic equivalent is a note , interval , or key signature which is equivalent to some other note, interval, or key signature, but "spelled", or named, differently...

ally 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.

Courtesy accidentals

Although a barline is nowadays understood to cancel the effect of an accidental (except for a tied note), often publishers will use a courtesy accidental (also referred to as a cautionary accidental or a reminder accidental) as a reminder of the correct pitch if the same note occurs in the following measure. This usage varies, although a few situations are construed to require a courtesy accidental, such as

• when the first note of a measure had an accidental applied to it 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.

Courtesy accidentals are sometimes enclosed in parentheses to emphasize their nature as reminders.

Publishers of jazz

Jazz

Jazz is a musical style that originated at the beginning of the 20th century in African American communities in the Southern United States. It was born out of a mix of African and European music traditions. From its early development until the present, jazz has incorporated music from 19th and 20th...

 music and some atonal music sometimes eschew all courtesy accidentals.

Microtonal notation

Composers of microtonal music

Microtonal music

Microtonal music is music using microtones—intervals of less than an equally spaced semitone. Microtonal music can also refer to music which uses intervals not found in the Western system of 12 equal intervals to the octave.-Terminology:...

 have developed a number of notations for indicating the various pitches outside of standard notation. One such system for notating quarter tone

Quarter tone

A quarter tone , is a pitch halfway between the usual notes of a chromatic scale, an interval about half as wide as a semitone, which is half a whole tone....

s, used by the Czech Alois Hába

Alois Hába

Alois Hába was a Czech composer, musical theorist and teacher. He is primarily known for his microtonal compositions, especially using the quarter tone scale, though he used others such as sixth-tones and twelfth-tones....

 and other composers, is shown on the 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 presuppose or merely the graphical shape of the accidentals. The most widely used system (created by Rauf Yekta Bey

Rauf Yekta Bey

Rauf Yekta Bey was a Turkish musician, musicologist and writer on music.-Biography:He wrote the first modern account of Turkish classical music available in a Western language .-References:* Turkmusikisi.com -...

) uses a system of 4 sharps (roughly +25 cent

Cent (music)

The cent is a logarithmic unit of measure used for musical intervals. Twelve-tone equal temperament divides the octave into 12 semitones of 100 cents each...

s, +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

Pythagorean comma

In musical tuning, the Pythagorean comma , named after the ancient mathematician and philosopher Pythagoras, is the small interval existing in Pythagorean tuning between two enharmonically equivalent notes such as C and B , or D and C...

 (about an 8th of the tempered tone, actually closer to 24 cents, defined as the difference between 7 octaves and 12 just-intonation fifths) as the basic interval. The Turkish systems have also been adopted by some Arab musicians.

Ben Johnston created a system of notation

Musical notation

Music notation or musical notation is any system that represents aurally perceived music, through the use of written symbols.-History:...

 for pieces in just intonation

Just intonation

In music, just intonation is any musical tuning in which the frequencies of notes are related by ratios of small whole numbers. Any interval tuned in this way is called a just interval. The two notes in any just interval are members of the same harmonic series...

 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. Between 2000 and 2003, Wolfgang von Schweinitz and Marc Sabat

Marc Sabat

Marc Sabat is a Canadian composer based in Berlin since 1999.-Works:He has made installations, video works and concert music pieces using acoustic instruments and, in some recent pieces, computer-generated electronics, drawing inspiration from investigations of the sounding and perception of small...

 developed The Extended Helmholtz-Ellis JI Pitch Notation, a modern adaptation and extension of the notation principles first used by Hermann von Helmholtz

Hermann von Helmholtz

Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...

, Arthur von Oettingen and Alexander John Ellis

Alexander John Ellis

Alexander John Ellis FRS was an English mathematician and philologist. He changed his name from his father's name Sharpe to his mother's maiden name Ellis in 1825, based on a condition for receiving significant financial support from a relative on his mother's side.- Biography :He was born...

 which is rapidly becoming adopted by musicians working in extended Just Intonation (for more details, see the Wikipedia article on Just Intonation

Just intonation

In music, just intonation is any musical tuning in which the frequencies of notes are related by ratios of small whole numbers. Any interval tuned in this way is called a just interval. The two notes in any just interval are members of the same harmonic series...

).

History of notation of accidentals

The three principal symbols indicating whether a note should be raised or lowered in pitch are derived from variations of the small letter b

B

B is the second letter in the basic modern Latin alphabet. It is used to represent a variety of bilabial sounds , most commonly a voiced bilabial plosive.-History:...

: the sharp

Sharp (music)

In music, sharp, dièse , or diesis means higher in pitch and the sharp symbol raises a note by a half tone. Intonation may be flat, sharp, or both, successively or simultaneously...

  and natural  signs from the square "b quadratum", and the flat sign from the round "b rotundum".

In the early days of European music notation (4-line staff Gregorian chant

Gregorian chant

Gregorian chant is the central tradition of Western plainchant, a form of monophonic liturgical music within Western Christianity that accompanied the celebration of Mass and other ritual services...

 manuscripts), only the note B could be altered (i.e. have an accidental applied to it): it could be flattened, thus moving from the hexachordum durum (i.e. the hard hexachord

Hexachord

In music, a hexachord is a collection of six pitch classes including six-note segments of a scale or tone row. The term was adopted in the Middle Ages and adapted in the twentieth-century in Milton Babbitt's serial theory.-Middle Ages:...

: G-A-B-C-D-E) where it is natural, to the hexachordum molle (i.e. the soft hexachord: F-G-A-B-C-D) where it is flat; the note B is not present in the third hexachord hexachordum naturale (i.e. the 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, signifying the B of the soft hexachord, that is, 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 B;
• both the natural sign and the sharp derive from a square b, signifying the B of the hard hexachord, that is, 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 German music notation the letter B designates B flat while the letter H, which is actually a deformation of a square B, designates B natural.

As polyphony became more complex, notes other than B needed to be altered in order to avoid undesirable harmonic or melodic intervals (especially the augmented 4th, or tritone

Tritone

In classical music from Western culture, the tritone |tone]]) is traditionally defined as a musical interval composed of three whole tones. In a chromatic scale, each whole tone can be further divided into two semitones...

, that music theory writers referred to as "diabolus in musica", i.e. "the devil in music"). The first sharp in use was F, then came the second flat E, then C, G, etc.; by the 16th century B, E, A, D, G and F, C, G, D and A were all in use to a greater or lesser extent.

However, those accidentals were often not notated in vocal part-books (but the correct pitches were always notated in tablature

Tablature

Tablature is a form of musical notation indicating instrument fingering rather than musical pitches....

). The notational practice of not marking implied accidentals, leaving them to be supplied by the performer instead, was called musica ficta

Musica ficta

Musica ficta was a term used in European music theory from the late 12th century to about 1600 to describe any pitches, whether notated or to be added by performers in accordance with their training, that lie outside the system of musica recta or musica vera as defined by the hexachord system of...

(i.e. "feigned music").

Strictly speaking the medieval signs and indicate that the melody is progressing inside a (fictive) hexachord of which the signed note is the mi or the fa respectively. That means they refer to a group of notes around the marked note, rather than indicating that the note itself is necessarily an accidental. Occasionally it is possible to see a mi-sign associated with e.g. a D. This could mean that the D is simply a D, but the note above E is now fa, i.e. it is one that is actually flattened to E flat (the 'accidental' in modern parlance).