"Historical editions are subdivided here according to content. ‘Collected editions’ refer to those publications that present a complete repertory, either the complete works of a single composer (also known as a ‘complete edition’ or ‘Gesamtausgabe’) or those multi-volume series in which the majority of individual volumes present a unified musical repertory derived from the same or from closely related original sources (also known as ‘Denkmäler’ or ‘monuments’). ‘Anthologies’ refer to historical publications of selections and excerpts from a variety of musical sources; these are subdivided into ‘extended anthologies’ (containing five or more volumes published over a period of five or more years) and ‘small anthologies’."
Sydney Robinson Charles, et al. "Editions, historical." Grove Music Online. Oxford Music Online. 25 Aug. 2008
Use the works lists in Grove or Heyer to locate individual items in a collected works set.
Collected editions for that composer will be listed at the top of the page. Note the abbreviation in brackets at the end of each listing.
Find the piece you are looking for in the works list. The right-hand columns will tell you where in the composer's collected works you can find that piece.
Collected editions are primarily classified in the M2s and M3s. Once you become familiar with the section you can scan it to find the set you are looking for, but otherwise you'll need to find the call number for the set you need. You can search the library catalog with the title you find in Grove, or Heyer, or, you can simply do a keyword search for [composer name] and works. This isn't precise, but will give you something to start with.
Caveat lector: sometimes we call things by nicknames, and you won't find those in the catalog. Perhaps the best example of this is the Neue Bach Ausgabe. This is what we call it, but the official name, and the name under which it is listed in the library catalog, is Neue Ausgabe sämtlicher Werke.
Thematic catalogues provide lists of composer's works in an organized fashion; many include incipits for the beginning of each work/movement. Often this is by opus number or chronology. Well-known examples are Otto Deutsch's Schubert thematic catalogue and Bach's BWV Bach Werke‐Verzeichnis (Index to Bach's Works). For a more detailed definition, see the entry in Grove. Thematic catalogs can also help you locate individual works in a composer's collected edition.
To find a thematic catalogue for a particular composer you can:
To find a thematic catalogue for a composer using Grove Online, first select the "Works" tab under the entry for that composer.
Thematic catalogues for that composer will be listed before the works list.