Bibliographie des Musikschrifttums

Enthusiastically endorsed by Morris Martin:

http://www.musikbibliographie.de/DB=1.86/LNG=EN/

"The Bibliographie des Musikschrifttums online (Bibliography of Music Literature on-line) is an international and interactive bibliography of literature on music. This bibliographic reference tool is edited by the Staatliches Institut für Musikforschung Preußischer Kulturbesitz, Berlin, and may be used free of charge. It is the continuation of the printed BMS volumes which stop with the report year 1988."