You closed the comments to an old post MacMost Now 631: Moving Your iTunes Media To an External Drive.
Does that video still apply to MacOS Mojave and latest iTunes (12.9.whatever)?
Or would you recommend a new improved way of doing this?
Only asking because that post and comments are 6 to 7 years old and things can change a lot with computers/software/apps in that time.
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Eric
I believe it is all still the same. You copy your media to an external drive. You would then remove the items from iTunes. You set iTunes to turn OFF "Copy files to iTunes Media folder when adding to library." And then you drag and drop into iTunes to add the items back so they are in your library, but the files are on the external.
I've been using Apple Music for years now, so I have no more "media" to manage. But I don't think this part of iTunes has changed at all.
Try it with a few songs to see how it goes. Then do the rest.