The Music Department of the Bibliothèque nationale de France has just incorporated the information from its old card catalogue (authors/composers/anonymous) into the online general catalogue http://catalogue.bnf.fr.
This covers holdings entered into the catalogues of the library from the sixteenth century through 1991, when the card catalogue was closed.
Update from Laurence Decobert:
With Sophie Renaudin in charge of the retroconversion, I wish to add some details about this converted catalogue. About 75% of the card catalogue of the Music Department is now converted (F-Pn card catalogue). The card catalogue of the Conservatoire (F-Pc) will be converted over the next 4 years. The whole catalogue will be available online at the end of 2016.