accidental
note whose pitch is not a member of the scale or mode indicated by the most recently applied key signature
double flat
accidental lowering the pitch of a note by two chromatic semitones
sori
symbol for a quarter step higher in tone in Iranian traditional music
sharp sign
musical sign (accidental) raising the pitch of a note by one chromatic semitone (factor 2^(1/12))
flat sign
musical sign (accidental) lowering the pitch of a note by one chromatic semitone (factor 2^(1/12))
double sharp
accidental raising the pitch of a note by two chromatic semitones
natural sign
musical sign (accidental) cancelling previous accidentals returning the frequency of the note to the natural/original value