The New York Public Library Music Division has extensive publications, sound recordings, reference and other materials about music. There are extensive holding in Jewish music. The catalog, called CATNYP, is available for searching online for complete holdings information. Finding aids to special collections are available in the library. Some finding aids have been digitized and are online (see below). The Lincoln Center Branch is located at Lincoln Center, just to the right of the front entrance to the opera. It contains much American theater music.
http://www.nypl.org/