Click Advanced Search...
to get the Advanced Search screen:
More search options are available by clicking Advanced Search.
The default WorldCat.org database includes a great number of specific databases. See the complete list here (or use the link below).
In addition, you can add still more databases to your search. You can also remove databases if you wish to search a smaller set or even a specific database.
For example, if you want to search a music topic you might want to deselect WorldCat.org and add the following: RILM, Music Index, Academic Search Premier.
Another example, if you want to search a public policy topic or issue, you might want to deselect WorldCat.org and add the following: PAIS International, Worldwide Political Science Abstracts, and Academic Search Premier.
You can add or subtract as many databases as you like. Be aware, though that some database search slower than others and might slow your search a bit.