Catalina, where is my Music Library? I can see it in Finder... but you can't!

From Empty/corrupt iTunes library after upgrade/crash - Apple Community.

macOS 10.15 Catalina

If you're missing expected content in the Music or TV apps after upgrading to Catalina try holding down option as you start either app and browse to the location of your previous iTunes Library to attempt the upgrade again. You may need to delete the file ~/Music/Music/Music Library first.

To be clear Catalina makes a new library file at ~/Music/Music/Music Library.musiclibrary however it will try to use the same media folder as was used by your old iTunes Library. Changing the active media folder doesn't make Music (or iTunes) rescan what is there, so if the library upgrade has gone wrong you need to restart it.

tt2

Try this method to locate it.

Switch libraries with the Music app or Apple TV app in macOS Catalina - https://support.apple.com/HT210230

Sorry, I don't use the new system so I can't check how things are arranged on a computer under it. I agree, the link I provided is somewhat scant on details.

Try selecting the "iTunes Library" file, your second image, top row, number 4 from the left.