The music holdings of the Bavarian State Library cover a broad spectrum of manuscript sources dating back to the Late Middle Ages. In a project funded by the German Research Foundation (DFG), the watermarks of these manuscripts are digitized using thermography technology and made available free of charge via the online services of BSB. Two historical inventory segments with polyphonic music are recorded. Firstly, there are the 170 choirbooks and manuscripts in choirbook notation, the majority of which date back to the performance material of the Munich Court Chapel of the 16th century. On the other hand, 70 handwritten tablatures and part books up to the middle of the 17th century are included. These manuscripts originate mainly from the library of the Augsburg alderman Johann Heinrich Herwart. Herwart's extensive library was acquired at the end of the 16th century, forming the basic stock of the music collection of the Munich Court Library, the predecessor institution of today's BSB. The music manuscripts have already been digitized by two DFG-funded projects and are included in their own portals in the Digital Collections. In addition to digitization, the watermarks are systematically recorded and integrated into the Watermark Information System (WZIS) and also provided by the Répertoire International des Sources Musicales (RISM) database.