The return, namely the later registration of a stock already in possession of the library, can be of greatest value for researchers. Within the joint financing of the Federal Government and the L nder the Mainz Academy is coordinating at present 17 long-term musicological editing and documenting projects which are not budgeted for at public institutions. 12 See Richtlinien-Empfehlungen zur Edition von Musikerbriefen. Academy of Sciences and Literature 1997. There they started to register the valuable and extensive collection of musicians' letters of the NB by means of a calendar catalogue.
Main emphasis is laid upon the musicians' unpublished works.
Through exact registration of the contents in form of calendars, connections are shown and information gained that with simple nominal cataloguing remains hidden.