This article presents new findings concerning a Latin carnival opera preserved in the collection from the Osek Cistercian monastery now held by the Czech Museum of Music in Prague under shelfmark XXXIV A 191. The opera has no title page, but in the manuscript librettos (shelfmark B 7478 and B 7479) it is called a ‘musical piece for passing the time’ (Facetum musicum / Musicalisches Kurtzweil-Spiel). The music is preserved in manuscript performing parts dated 1738. When the opera was performed in 2004 it was discovered that this is not a work by an unknown Czech composer but rather a retexted pasticcio of Italian operatic arias. Identified so far are the overture (sinfonia) and six arias, coming from the following operas: G. F. Handel’s Agrippina, Antonio Lotti’s Isacio tiranno (identified based on the score of Carmine Giordani’s La Vittoria d’Amor coniugale, which is an arrangement of that opera), Lotti’s Il tradimento traditor di se stesso, and Antonio Vivaldi’s Orlando finto pazzo. It has not yet been determined who arranged the work. The present article includes a thematic catalogue of arias, as well as a comparison of the texts of the identified arias in their adaptations as opposed to their original forms.