Thanks for the suggestion.
I’m reasonably tech savvy for a non pro, but this is a bit too advanced for me to attempt on my own.
Before the iPhone 11 purchase, I started with everything complete and mirrored on the computer and the old phone, as well as the iPad.
Songs, collections, all the same. — The iTunes libraries including the mp3 files, in all my devices, MacBook OS 12.4 Sierra, iPad iOS on 12.4, old iPhone iOS on 12.4. All my music synced beautifully.
It was the transfer to the iPhone 11 and iOS 13.3.1 that created the problem.
Not everything came through from my old phone iOS 12.4, and when the techs at Apple tried to unearth the missing music, and even tried a transfer from my iTunes computer files through a ‘neutral’ computer, only some but not all, of the music came through. Then the library on the computer lost music to mirror the iPhone likely because iCloud sync was still on.
My music sources with the original iTunes music folder, populated completely as before, are now the iPad and the external drive
If I’m understanding you correctly, the music on the MacBook OS Sierra, disappeared when the iPhone 11’s incomplete music was synced to the computer’s complete music folder. Meaning the music library on the iPhone took precedence over the music folder on the computer and not the other way around.
So if I reinstall iTunes music on my computer from the folder in the external drive, am I understanding correctly that the iPhone 11 will destroy it again unless I start with an empty iTunes folder on the iPhone? And that’s only done with a third party app?
And during this process the iCloud sync should be turned off?
sorry for all the questions. I want to be sure I’m understanding everything you’re suggesting.