<P> 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 on the right . </P> <P> In the 19th and early 20th centuries, when Turkish musicians switched from their traditional notation systems--which were not staff - based--to the European staff - based system, they refined the European accidental system so they could notate Turkish scales that use intervals smaller than a tempered semitone . There are several such systems, which vary as to how they divide the octave they presuppose or the graphical shape of the accidentals . The most widely used system (created by Rauf Yekta Bey) uses a system of four sharps (roughly + 25 cents, + 75 cents, + 125 cents and + 175 cents) and four 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 eighth of the tempered tone, actually closer to 24 cents, defined as the difference between seven octaves and 12 just - intonation fifths) as the basic interval . The Turkish systems have also been adopted by some Arab musicians . </P> <P> 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 create just tuning in other keys . Between 2000 and 2003, Wolfgang von Schweinitz and Marc Sabat developed the Extended Helmholtz - Ellis JI Pitch Notation, a modern adaptation and extension of the notation principles first used by Hermann von Helmholtz, Arthur von Oettingen, and Alexander John Ellis that some other musicians use for notating extended just intonation . </P> <P> The three principal symbols indicating whether a note should be raised or lowered in pitch are derived from variations of the small letter b: the sharp (♯) and natural (♮) signs from the square "b quadratum", and the flat sign (♭) from the round "b rotundum" b . </P>

Sign is used in musical notation to cancel a previous sharp or flat sign