A contrafact is a musical work based on a prior work. Wikipedia

Musical work based on a prior work. In jazz, a contrafact is a musical composition consisting of a new melody overlaid on a familiar harmonic structure. Wikidata

A new musical composition built out of an already existing one, most often a new melody overlaid on a familiar harmonic structure. An important part of the development of bebop. Contrafacts are not to be confused with musical quotations, which borrow rhythms or melodies from an existing composition. Wiktionary

Musical composition. Wiktionary (translation)