A courtesy accidental, also called a cautionary or reminder accidental, is one that, according to the rules of accidental occurrence, isn’t strictly necessary before a note. But there are times when the composer wants to remind the player that an accidental is (or is not) in effect for a particular note. For example, in a measure containing several E accidentals, the first E in the next measure often has a courtesy natural attached, even though the E is technically canceled in the new measure. See also Cautionary Accidentals..
