What does courtesy accidental mean in music?

Notation & reading

Courtesy accidental

Also: cautionary accidental, reminder accidental

A courtesy accidental is a sharp, flat, or natural printed to confirm a pitch the reader might otherwise doubt, often in parentheses, and it changes nothing about how the note is played.

Accidentals last to the end of the measure, so the first note of the following bar reverts to the key signature. A good editor prints a courtesy natural on that note anyway, because a player mid-phrase should not have to reason about barline rules at speed.

They also appear after a key change, after a passage that used many accidentals, and on the same pitch in a different octave, all situations where an experienced reader hesitates. Parentheses mark them as reminders rather than new instructions.

For a student, the useful lesson is the inverse: where a courtesy accidental is absent, the rule still applies. The barline cancels; the key signature returns.

Accidental: An accidental is a sharp, flat, or natural sign placed before a note to raise, lower, or restore its pitch for the remainder of that bar.
Key signature: A key signature is the group of sharps or flats written at the start of each staff line, indicating which notes are consistently altered throughout the piece.
Enharmonic: Two notes are enharmonic when they sound the same pitch but are written differently, such as F sharp and G flat.
Sight-reading: Sight-reading is playing a piece of music accurately on first sight, without having practised it beforehand.

Every term in this glossary is taught in context somewhere in Arco's curricula, on the staff, on the keyboard, and on your own fingerboard at the same time.

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