Notes that belong to the diatonic scale relevant in a tonal context are called diatonic notes. Notes that do not meet that criterion are called chromatic notes or accidentals. Accidental symbols visually communicate a modification of a note's pitch from its tonal context. Most commonly, the sharp symbol () raises a note by a half step, while the flat symbol () lowers a note by a half step. This half step interval is also known as a semitone (which has an equal temperament frequency ratio of ≅ 1.0595). The natural symbol () indicates that any previously applied accidentals should be cancelled. Advanced musicians use the double-sharp symbol () to raise the pitch by two semitones, the double-flat symbol () to lower it by two semitones, and even more advanced accidental symbols (e.g. for quarter tones). Accidental symbols are placed to the right of a note's letter when written in text (e.g. F is F-sharp, B is B-flat, and C is C natural), but are placed to the left of a note's head when drawn on a staff.
notes that BelOnG to THe dIatOnic scAle relEvanT in a TOnal context aRe cAlLEd DIATONic Notes. NoTEs ThAt dO nOt mEeT tHat criteRiOn ARE cAlLed chROmaTiC NOTES Or acCIdeNtals. aCcidEntal sYmboLs visuallY commuNicatE A modificatIOn oF a nOTe's pITCh from ItS TOnAl conteXt. MOst Commonly, tHE sharp sYmBol () raiSeS a notE bY A half sTEp, whIle the fLat symbOl () lowers A Note by A halF Step. THis half SteP INtervAl iS ALSo knowN as a semiTone (whicH Has an EQUAl teMpEramenT frEquency RatiO of ≅ 1.0595). THe natural SyMbOL () iNdicateS thaT Any pReviOuSly AppLIed acCidentAls ShoULd Be cancellED. ADVAnCed musIciaNS usE the doublE-sharp syMbOl () To raise the pItCh by tWo seMitonEs, thE DoubLE-flat sYmbOL () tO loweR iT BY twO SemItonES, and even morE advancEd AccideNtaL symbOls (e.G. fOR quArTer tOnEs). accidentaL symbols aRe pLaced to the riGHt of a nOte's LeTTeR When wrItTen IN texT (E.g. f Is f-sharP, b is b-fLAt, ANd c is C nAturaL), BuT Are placed to the lEFt oF a note's hEad When drawn ON a stafF.