Upgrade your iTunes library in macOS Catalina
When you open the Apple Music app for the first time in macOS Catalina, your iTunes library is upgraded so you can use it with the new apps. If you have multiple iTunes libraries, you need to upgrade each library before you can use and switch between them in macOS Catalina.
Switch to another iTunes library
- Hold down the Option key, then open the Music app.
- In the window that appears, click Choose Library.
- Select a library, then click Choose.
Learn more about what happens when you upgrade another iTunes library.