Natural sign
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In musical notation, a natural sign 
is a sign used to cancel a flat or sharp from either a preceding note or the key signature. The Unicode character '♮' (U+266E) may display as a natural sign on some computers. Naturals are assumed (by default) in key signatures and mentioned only in key signature changes.
In highly chromatic and atonal music, to prevent any ambiguity in performance, natural signs may be placed in front of any note that is to be neither flattened (flatted) nor sharpened (sharped).
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