Most databases have something that they call "Controlled Vocabulary." This means that there is a particular "correct" word to use in order to get the largest number of related results.
For example, if you needed to find Grieg's "In the hall of the mountain king." This is not actually the controlled name for this piece because the title was originally in another language. So in order to get the most results for it, you would have to do a little investigating to widen the search.
An area to look for information like this is in the "Subjects" field inside a search result. This means that your first search might not be as good as the following ones, but after figuring out what the "official" name for your piece is your results should be more accurate.
This database does have a feature called "apply related words" that you can check in the "Search Options" area, however this is not necessarily helpful when you are working in the music field.