Répertoire International des Sources Musicales (RISM)
This International Inventory of Musical Sources is an international project which aims to catalogue all surviving musical sources from the earliest ones to about 1850. This is a mammoth task, so this online resource is still work in progress. None the less, RISM remains an essential tool for the location of primary sources.
There are two complementery online resources linked to RISM which you may need to consult:
1. Click on the following link to navigate to an English interface: RISM. Sometimes yu may need to 'remind' the user interface that you would like English by clicking the appropriate icon.
2. The second link is: RISM2