Répertoire International des Sources Musicales (RISM)
The Répertoire International des Sources Musicales (RISM) is an international non-profit organization dedicated to comprehensively documenting existing music sources from around the world. The RISM database offers the most comprehensive documentation on music printing and music manuscripts from the period 1600 - 1800, as well as on librettos and theoretical writings on music. The database is still growing. Thanks to monthly updates, about 30,000 new records will be added per year.
Additional link for access