iTunes can't seem to locate missing files that are in the same folder as the first file I locate

Thanks for the reply.

Things have moved on a bit since I wrote the first post, but to answer your questions:

1 The path in prefs > advanced was the shorter of the two I mentioned in the original post.

2 The path in the get info panel for a missing track leads to a folder within the hidden folder "dropbox.cache". Unfortunately, when I show hidden folders & look in dropbox.cache that particular sub-folder is not there.

3 The true path of the same file leads to the correct location in my music folder.

However, I've since followed your instructions about split libraries & now have a correctly built library that, as far as I can tell, is portable & all sits in one place, within my dropbox folders.

I did this manually (& very carefully) but I can now see that the path in "prefs > advanced" is the same as the path in a given "get info" panel, (with the addition of the artist & album folders, of course).

What I now need to do is to fix the 5,000 odd tracks that still have exclamation marks because when I first changed the location in the advanced tab, having made the library portable, iTunes did the thing with the little grey progress bar of rebuilding the library, but this doesn't seem to have fixed them.

I'm unsure as to which of the techniques to try as I don't want iTunes to re-organise any of the music files within the "iTunes media > music" folder or bring anything in from outside, as I have a lot of unsorted music that I've not yet brought into iTunes.

Any thoughts?

Well, I got impatient & went ahead & did it anyway. But thanks for coming back to me. Apart from the playlist I use to sync my phone, (as it’s easier to gauge the size against the capacity of the phone), I don’t use any of those other things.

It did, for some reason, create maybe twenty or so playlists randomly for random albums plus a few empty ones. Not sure why that would be. Maybe there’s a little data file in with some of the albums that refers to a playlist?

Anyway, all back to normal. The instructions to make the library portable were great! (Although my tiny brain was somewhat bamboozled by the points being numbered but referred to in the text alphabetically. But I got there in the end.)

It occurs to me that I could delete my entire library, choose keep the songs when prompted & then just go "apple + o" on the music folder & re-add everything?