Among the holdings of Hamburg’s Staats- und Universitätsbibliothek Carl von Ossietzky is an anonymous fifty-two-page score headed ‘Serenata à 4’, described in the corresponding catalogue entry by its former owner, German musicologist Friedrich Chrysander (1826–1901), as a ‘cantata for the funeral of the English king William III of Orange, 1702’. But both the work’s text and the recent identification of the manuscript as being in the hand of Johann Sigismund Cousser (1660–1727) call for a reassessment of this serenata’s provenance, situating it in either England or Ireland between Cousser’s arrival in London on Christmas Day 1704 and the end of Queen Anne’s reign in 1714. Over the course of the two decades he resided in Ireland, from 4 July 1707 until his death, Cousser was responsible for the composition and musical direction of one ode and more than twenty serenatas, the majority of which were commissioned by the viceregal court at Dublin Castle for state celebrations of the reigning monarch’s birthday. Taking printed librettos, contemporary newspaper reports, Cousser’s own commonplace book and two further surviving manuscript scores as its primary evidence, this study seeks to establish a likely location and occasion for the performance of the ‘William III’ serenata within Dublin’s musical life during the early eighteenth century. In their choice of terminology, compositional style and performance practices, Cousser’s serenatas, which may have incorporated elements of theatrical staging and dancing, reveal his extensive Continental experience, and they can be seen to have functioned in part as an operatic substitute, presumably reflecting the limited financial resources of Dublin high society.