accidentali

Accidentali, in music notation, are symbols placed before notes to indicate a pitch alteration relative to the prevailing key signature. The common accidentals are sharp (raising a note by one semitone), flat (lowering by one semitone), and natural (canceling a previous accidental or the key signature). In addition, composers use double sharps and double flats to raise or lower a note by two semitones. Each accidental applies to the specific note letter within the current measure, and typically remains in force for the rest of that measure unless canceled by a natural or by the barline. Accidentals do not automatically carry to the same note in a different octave; a separate accidental is usually written for other octaves if needed.

In standard Western notation, accidentali are tied to the staff position rather than globally to a pitch class; thus a note on the F line with a sharp in one measure will become F sharp for the remainder of that measure, but F sharp in the next measure resets to the key signature unless notated again. The use of accidentals allows modulations and chromatic passing tones without changing key signature.

The term accidentali (plural) is used in Italian and in music-theoretical texts to describe these symbols. They are also accompanied by courtesy accidentals, which are reminders that an earlier accidental or key signature continues to apply.

Historical note: accidentals emerged in medieval and Renaissance notations and became standardized in Baroque and later notation, enabling flexible chromatic harmony.