Yet if you don't check it, you could end up later on restoring an i Tunes backup and discovering that these other files were not copied.So in i Tunes on your Mac, go to the Files menu, choose Library and then Organize Library.You've got years upon years of music, film and TV clogging up your library and you're not really sure where it all is.Take some time now to let your Mac sort out your i Tunes library before you move to mac OS Catalina.You have to tell the i Tunes app where you've put it all, but once you've done that, everything is good.https://appleinsider.com/articles/18/03/05/how-to-free-up-your-macs-internal-storage-by-moving-your-itunes-library-to-an-external-drive Conceivably there is a minuscule speed difference between i Tunes retrieving data from your Mac's internal SSD and an external hard drive, but as long as the music or the video plays, you don't notice.And then you can back it all up by dragging the entire i Tunes folder to another external drive.
It means that whatever you or i Tunes has ever done with any of your media, you straighten it out now.
Apple keeps everything, all of your media and all of the information about it, in the one i Tunes folder so as long as that's safely backed up, it can be safely restored.
If you don't have the room for these duplicates on your internal drive, the default location that i Tunes uses, there is something you can do about it. You don't just run out of storage space through this duplication and consolidation.
Most of us have big enough i Tunes libraries that they are taking up a significant proportion of our internal drive.
The average i Tunes library is so big that we have previously shown you how to move the entire thing over to an external drive.
Search for consolidating itunes:
"i Tunes in the Cloud is not a backup service," it says, "and having a local copy (a copy downloaded to a computer) is the only way to back up your purchased media." https://support.apple.com/en-us/HT201625 Then choose the Account menu.