Music Cataloging at Yale [1] ♪ Preferred titles [2]
See also Thematic catalogs [3]
Many composer's works are assigned work (or thematic index) numbers [4] in addition to or in place of opus or serial numbers.
For a list of thematic indexes currently being used in the creation of authorized and variant access points in the Library of Congress/NACO Authority File (LC/NAF), see the Music Library Association Cataloging and Metadata Committee's Thematic Indexes Used in Library of Congress NACO Authority Files [5]
Links
[1] http://web.library.yale.edu/cataloging/music
[2] http://web.library.yale.edu/cataloging/music/preferred-titles
[3] http://web.library.yale.edu/cataloging/music/thematic-catalogs
[4] http://web.library.yale.edu/cataloging/music/thematic-catalogs#themnumb
[5] https://cmc.wp.musiclibraryassoc.org/thematic-indexes-used-in-library-of-congress-naco-authority-files/