It might be in a collection.
Shorter works like songs, instrumental solo pieces, etc., are often published in collections (songbooks, anthologies, CD albums). To locate a work that might be in such a collection, try the strategies described for "Short works" and "Works with opus numbers" under Classical Music.
Try the composer’s collected edition.
See the tips below.
For many composers, their complete works have been published in a single scholarly edition (called a collected edition).
In these editions, the variant readings in the primary sources are shown, either in the main volumes or in separate supplementary volumes.
Some of these editions are still in progress, so you may find that a specific work has not yet been published in the composer’s collected edition.
Finding a composer’s collected edition
To identify any collected edition(s) that may have been published for a composer, look up the composer's worklist in Oxford Music Online (available on our "Databases" page). The composer's collected edition(s) will be cited at the top of the worklist. (Foreign terms you may see that mean "collected edition": Werke, Samtliche Werke, Gesamtausgabe, Opere, Oeuvres.)
To see if ZSR Library owns a composer’s collected edition, see the following list:
http://guides.zsr.wfu.edu/composers-collected-editions
This provides links to the Library’s catalog record. There, you can find out:
Finding a specific work in a composer’s collected edition
You can do this several different ways:
Check the composer's worklist in Oxford Music Online (available on our "Databases" page). For each work, the volume number in the collected edition is given.
Online versions will have their own hyperlinked table of contents.
Or, consult the following separately-published indexes, shelved in the Reference room:
Websites that contain composers' collected editions