The "Dictionary Catalog of the Music Collection" (colloquially known as the "Black Book Catalog") is a photoreproduction of the Music Division's card catalog as it existed at the beginning of 1972. (At that time the Library switched to online cataloging and card catalog was closed with no new additions.)
Although all of the books listed in the Dictionary Catalog are in the online catalog, nearly all of the musical scores are NOT listed in the online catalog. One must consult this Dictionary Catalog to see the scores the Music Division acquired and cataloged prior to 1972 (approximately 120,000 scores).
From the late 1920s through about 1954, the Music Division also made entries for significant articles in important periodicals. Although some of these periodicals (such as Musical Quarterly and Music and Letters) are covered by electronic resources such as JSTOR, many of these periodicals especially from the 1930s and 1940s have neither been digitized nor indexed. Thus the Dictionary Catalog is a valuable resource for seeking articles from the late 1920s through the early 1950s.
There are also miscellaneous items listed in the Dictionary Catalog which are not listed in the online catalog, such as music school catalogs, dealers' catalogs and publishers' catalog.
It should be remembered that the Music Division collected an enormous about of ephemera including clippings, programs, sheet music and iconography. None of these items are listed in the Dictionary Catalog.
Unfortunately the quality of reproduction did not lend itself to OCR (optical character recognition) so the digitized version of the Dictionary Catalog is not keyword searchable.