Cecil Sharp (1859-1924) was a friend of Oppé and his wife Valentine, and was in regular contact with both. Sharp was a musician, author and folklorist, with particular interests in the collection of traditional folk songs from rural England and America and the recovery and popularisation of traditional folk dances. In 1911, Sharp founded the the English Folk Dance Society to pursue these interests.
Professionally, Oppé and Sharp only collaborated on one book project, published in the year of Sharp's death, which concerned history of dance and its depiction in works of art: Sharp, C.J. and Oppé, A.P. (1924) The dance : an historical survey of dancing in Europe. London: Halton & Truscott Smith, Ltd. [Oppé's annotated copy is available in the Paul Mellon Centre library, see URL below]. The text uses an older essay on the subject by Sharp, with Oppé providing the plates, which are depictions of dance in drawings and paintings.