http://www.rism.harvard.edu/RISM/
This RISM (RÄpertoire International des Sources Musicales) Office collects information from libraries in the United States about music manuscripts, printed music, and libretti from the years 1580-1825. The Office makes available cataloguing for manuscripts and libretti through Internet-accessible databases in the United States free of charge. It also maintains several additional information files that may be of interest to librarians and scholars. Online resources include the RISM-US Music Manuscripts Database, RISM Libretto Project, RISM Names Authority File RISM-L, and the RISM news list maintained by the US RISM Office.