Accidental (music)

In musical notation, an accidental is a symbol used to alter a specific pitch. These marks tell a musician to change a note from its standard sound. Accidentals are vital because they allow for a wider variety of tones and melodies. Without them, music would be limited to the basic notes found in a key signature. Most musicians interact with accidentals daily to navigate complex musical landscapes.

The most common accidentals are the sharp, the flat, and the natural. A sharp raises a note's pitch by one semitone, which is the smallest interval in standard tuning. A flat lowers a pitch by one semitone. To cancel these changes, musicians use a natural sign to return the note to its original state. Some compositions even use double sharps or double flats. These symbols alter a note by two semitones instead of one. Triple accidentals are extremely rare and change a note by three semitones.

Accidentals follow strict rules regarding how long they last. In standard notation, an accidental applies to the note immediately following it. It also applies to any subsequent instances of that same note within the same measure. The effect usually ends when a musician reaches a barline. However, an accidental can carry over a barline if a note is tied to another. A tie connects two notes so they sound as one continuous tone. In these cases, the accidental continues to apply to the tied note.

Sometimes, notation can become confusing, requiring courtesy accidentals. These are also called cautionary or reminder accidentals. They are used to prevent mistakes when a note might be misunderstood. For example, they are used if a note in a new measure is the same as a note with an accidental in the previous measure. They can also appear after a tie carries an accidental across a barline. Some publishers put these signs in parentheses to keep the score clean.

The history of these symbols traces back to medieval music. Modern accidentals actually derive from different forms of the lowercase letter "b." In Gregorian chant manuscripts, two versions of "b" were used to signify different pitches of the note B. The round "b," or "b rotundum," eventually became the flat sign. The square "b," or "b quadratum," diverged into the sharp and natural signs. In French, the flat is called "bémol," meaning "soft b." The natural and sharp signs come from "bécarre," meaning "square b."

This system grew from a practice called musica ficta in the late 12th century. During the High Middle Ages, music was often based on the hexachord system. This system used groups of six notes called hexachords. Musicians sometimes encountered "undesirable" sounds called dissonances. To avoid these, they began using "feigned" or "false" notes. At first, this only involved flattening the note B to move between different hexachords. This practice eventually evolved into the formal accidental system used in modern notation.

Different musical traditions have developed unique ways to handle pitch. In the 19th and 20th centuries, Turkish musicians adapted European staff notation. They refined the system to include intervals smaller than a standard semitone. One major system, created by Rauf Yekta Bey, uses four specific sharps and four flats. These do not match standard European sharps or flats. Similarly, composers of microtonal music use special notations for very small pitch changes. These systems allow musicians to express scales that fall outside the standard 12-tone system.

Modern music has also changed how accidentals are written to improve readability. In atonal music, accidentals appear very frequently. This can make standard notation look cluttered and difficult to read. Because of this, some musicians use an alternative system described by Kurt Stone. In this method, accidentals affect only the notes they immediately precede. This reduces the number of natural signs needed on the page. In some atonal scores, every single note receives an accidental. This treats every pitch as having equal status rather than being an inflection of a natural note.