This volume features six double-choir motets attributed to Iacobus Handl-Gallus that circulated exclusively in manuscript form during the 16th and 17th centuries. These compositions were never published, either during the composer's lifetime or posthumously, and have survived solely in manuscript sources now housed in various libraries and music archives across Europe. Presented here for the first time in a modern critical edition, these motets are accompanied by a detailed introduction and critical commentary. The introduction explores the complex issues surrounding the transmission of the works, including the origins and historical context of the manuscripts.The critical reports provide an in-depth analysis of the philological challenges posed by the sources.