I focus on a network of related materials whose transmission spans over 100 years. Preserved as a clausula in the early-13th-century Florence MS, the two-voice motet Ne sai que je die/IOHANNE appears in later sources (sometimes with alternative Latin texts) and as a three-voice polytextual motet with added ‘Franconian’ upper voice using many short notes, made possible by late-13th-/early-14th-century advances in rhythmic notation. It appears too, with adapted Latin moralising text, in the early-14th-century Roman de Fauvel, a vernacular romance with musical interpolations. The case study – involving multiple genres, languages, notational technologies, and manuscript contexts – is the basis for final reflections on notational styles, ideas of originality and authorship, and the afterlife of 13th-century music. It suggests alternative emphases to accepted chronological models. Why did this musical material's popularity continue over a century after its conception? How did text and music change as it was accommodated in different generic contexts and notational systems? How might the ‘old’ 13th-century musical style have been perceived and updated in new 14th-century contexts?