In modern notational practice, [[accidentals]] apply only to subsequent pitches in the same octave. However, this particular nuance of music notation remains widely misunderstood. One likely reason is that, although some publishers distinguish courtesy accidentals from required accidentals through the use of parentheses, many publishers do not. In **Example 1** below, the fourth note of measure 1 is understood to be E♮ and not E♭. Thus, measures 1 and 2 are played and sound exactly the same. The natural in the second measure is not required but a courtesy accidental. **Example 1.** Courtesy accidental. ![[example courtesy accidental.png]] If the fourth note is instead to be understood as E♭, then an accidental is required, as shown in the first measure of **Example 2**. Thus, the natural in the second measure is the courtesy accidental, not the second flat in the first measure. **Example 2.** Required accidental vs. courtesy accidental. ![[example required accidental vs courtesy accidental.png]] The misconception that accidentals apply across octaves likely arises from situations such as these. Courtesy accidentals have become so commonplace that their absence creates opportunities for misunderstandings of notational conventions to creep in. In this case, the absence of an expected courtesy accidental in the first measure of **Example 1** leads some to erroneously believe that the flat on the first beat applies to every E in the measure. This view is misguided but understandable given the prevalence of courtesy accidentals. For those who still have doubts, I recommend consulting Elaine Gould’s *Behind Bars*, widely considered the most comprehensive and authoritative guide available on music notation.^[Elaine Gould, _Behind Bars: The Definitive Guide to Music Notation_ (London: Faber Music, 2011).] As she writes: > An accidental holds good for the duration of a bar. It applies only to the pitch at which it is written: each additional octave requires a further accidental.^[Ibid. 78.] Regarding octave displacement she further clarifies: > A pitch that occurs at a different octave should be confirmed or altered with an accidental . . . ^[Ibid. 82.] And regarding courtesy (or cautionary) accidentals: >. . . though not strictly necessary . . . [c]autionary accidentals confirm the pitch of a note that might otherwise be questioned . . . ^[Ibid.] As Gould explains, courtesy accidentals are not strictly required, but have become an expected convention to avoid ambiguity. Thus, the absence of courtesy accidentals when expected can contribute to misunderstandings that eventually reshape how required accidentals are interpreted. It also bears reminding that the conventions surrounding accidentals are historically and culturally situated. There are no universal rules or single authoritative body governing the interpretation of music notation. Notation is merely a means through which composers express musical ideas. If ambiguity arises, the best solution is to reach out to the composer for clarification. When that is impossible, we must do our best to reconstruct the performance practice and notational conventions of the composer’s time using whatever evidence we have at our disposal, including knowledge of the musical language and syntax of the time. After all, the ambiguity may simply arise from a misprint or an error on the composer's part.