I have one library for DJ tracks (Serato), and another library for listening music.

To create or use a different iTunes library:

1. If iTunes is open, quit it.
2. Hold down the Option key while you open iTunes.
3. In the dialog that appears, do one of the following:
4. To create a new library, click Create Library.
5. To choose a different library, click Choose Library.

Apple: Using multiple iTunes libraries