moving music to external drive

Not really rocket science. It's a matter of dragging a folder from one place to another (drive to drive so that will copy it), then holding down a key on your keyboard while starting the Music app one time and choosing the place you just copied the folder to get it to start using that place. Apart from the copying the whole process should take about 4.35 seconds.

Move the folder ~/Music/Music to /Volumes/<External Drive>/ then hold down option as you launch Music, click the button to choose a library, and open the library file /Volumes/<External Drive>/Music/Music Library.musiclibrary. You can repeat with the TV app, ~/Movies/TV going to the external drive and then accessing /Volumes/<External Drive>/TV/TV Library.tvlibrary by holding down option as you launch. Note with Catalina you won't have control over where Podcasts, Books, or Audiobooks are stored.

tt2

Note with Catalina you won't have control over where Podcasts, Books, or Audiobooks are stored.

tt2

If I recall correctly, tt2 said in an earlier post you could try re-assigning these as music files if you are desperate for space. It may take a bit or work though.

Yes, if you move the Music folder from <User>/Music/Music to <External>/Music then it only takes up room on the external drive. Use Cmd-drag-drop to move the folder from one location to the other, or copy first, then delete the original.

tt2