false note

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false note (plural false notes)

1. (music) An incorrect note which is sung or played in a musical performance.
   • 1819, Washington Irving, “The Lovers”, in Bracebridge Hall:

     Sometimes he even thrums a little on the piano, and takes a part in a trio, in which his voice can generally be distinguished by a certain quavering tone, and an occasional false note.

   • 1860, Wilkie Collins, chapter 15, in The Woman in White:

     Her fingers wavered on the piano—she struck a false note, confused herself in trying to set it right, and dropped her hands angrily on her lap.

2. (idiomatic, by extension) In a remark or narrative, an indication (as discerned by the listener or reader) of untruth, insincerity, or inconsistency.
   • 1900, Fergus Hume, “Mr Baltic, Missionary”, in Bishop Pendle: Or, The Bishop’s Secret, Chicago, Ill., New York, N.Y.: Rand, McNally & Company, →OCLC, page 202:

     is words were grave, his manner was earnest, and his speech came from the fulness of his heart. If there had been a false note, a false look, Harry would have detected both, […]

   • 1990 September 14, Janet Maslin, “Movie Review: White Hunter Black Heart (1990)”, in New York Times, retrieved 16 April 2015:

     The screenplay . . . even suggests that this contributed to the false note on which The African Queen actually ends.

   • 2010 December 10, Brigitte Weeks, “Book World: From its opening car crash, Anita Shreve's character-driven Rescue is worth the ride”, in Washington Post, retrieved 16 April 2015:

     Shreve creates a little world, peoples it with believable characters, and puts them through agonizing and joyful moments without a false note or a dissonant figure of speech.

3. (idiomatic, by extension) In a non-verbal display or presentation, an indication of incongruity or inappropriateness.
   • 2009 February 20, Hilary Alexander, “London Fashion Week: Caroline Charles”, in Telegraph, UK, retrieved 16 April 2015:

     The only false note in an otherwise classic and elegant collection was the gratuitous flash of black fishnet stockings and suspenders under otherwise unremarkable paisley and floral shirts.

• strike a false note, hit a false note