Definition of "crotchet"

The crotchets and quavers are dancing up and down the stave like little black boys on a fence.

1920 August 27, Katherine Mansfield [pseudonym; Kathleen Mansfield Murry], “The Wind Blows”, in Bliss and Other Stories, London: Constable & Company, published 1920, pages 140–141

Either Doctor Denman or an old Woman would have waited—but since the horrid death-doing Crotchet has been found out, & its use permitted—Oh! many & many a Life has been flung away.

1797 September 1, Hester Lynch Piozzi, Thraliana

Thou who walkest in a vain shew, looking out with ornamental dilettante sniff and serene supremacy at all Life and all Death; and amblest jauntily; perking up thy poor talk into crotchets, thy poor conduct into fatuous somnambulisms; [...] dost thou call that "liberty!"

1843 April, Thomas Carlyle, “Democracy”, in Past and Present, American edition, Boston, Mass.: Charles C[offin] Little and James Brown, published 1843, book III (The Modern Worker), page 124

He ruined himself and all that trusted in him by crotchets that he could never explain to any rational man.

1847, Thomas De Quincey, “Secret Societies”, in Tait's Edinburgh Magazine

Their little Shed, ſcarce large enough for Two, / Seems, from the Ground increas'd, in Height and Bulk to grow. / A ſtately Temple ſhoots within the Skies, / The Crotchets of their Cot in Columns riſe: [...]

1717, John Dryden, “Book VIII. [The Story of Baucis and Philemon.]”, in Ovid’s Metamorphoses in Fifteen Books. […], London: […] Jacob Tonson, […], page 287

The nimblest crotcheting musician

a. 1631 (date written), J[ohn] Donne, “(please specify the title)”, in Poems, […] with Elegies on the Authors Death, London: […] M[iles] F[lesher] for Iohn Marriot, […], published 1633