Chansonniers copied from the thirteenth and the fourteenth centuries are the earliest extant sources to include an extensive corpus of lyrics in European vernacular languages. However, contemporary literary sources refer to the existence of earlier books of vernacular lyrics, and a handful of notated lyrics survive from as early as the twelfth century. This article explores a certain type of notated song that predates the relatively well-documented chansonnier tradition by some decades, specifically focusing on the case study of the crusader recruitment song Chevalier mult estes guariz (RS 1548a), composed around the mid-1140s. Probably the earliest extant copy of an Old French lyric (with or without musical notation), this unicum is distinct from songs of the kind preserved in the chansonniers in several respects, especially in its musical form, its manuscript appearance and its intended use in the Middle Ages. I examine this song from several angles, including its crusading theme, provenance, authorship, manuscript presentation, musical construction, intended audience, and the broader contexts of its composition and copying. Such close examination of a single song not only offers insights into the context of an early tradition of written-out vernacular monophony but also casts new light on the origins of the later chansonnier tradition.