Q: XML Legacy Issues with "External Library"

TL;DR: When an iTunes library is anywhere other than the default path of user's music the active XML file will normally be called iTunes Library.xml (it takes the same name as the .itl file.) You should delete any iTunes Music Library.xml you copied over when rearranging your library and make sure that your third party tool is accessing the correct XML file.

See Make a split library portable for gory details.

tt2

Checked my active XML. All the playlists are there. In my case the XML is about 5 times the size of the ITL. To make sure you're looking at the right files try the script iTunesInfo.

See the my earlier link for information on library structure. The "Rearrange files" option will be greyed out if the media folder is in the new layout. Information on the layout is stored in .iTunes Preferences.plist inside the media folder.

tt2

I suspect that you are misunderstanding the relationship between the iTunes database (the iTunes Library.itl file) and the XML representation of some of its content.  When iTunes is running it has exactly one library, determined by the iTunes Library.itl file loaded on startup.  Any other libraries that you may be able to see in iTunes will be those on other systems on your local network, via Home Sharing or Family Sharing.  The XML file (which as tt2 notes may be named iTunes Library.xml or iTunes Music Library.xml, based on your configuration) is simply a serialized version of your current library, intended for use by third-party applications.  In normal operations iTunes only writes to the XML file (every time you make a change to the library) - editing the XML file will make no difference to any of iTunes' functions, and will be overwritten anyway when iTunes runs.  You can always delete any .xml files that are in the same folder as the current iTunes Library.itl and will see that one is recreated as soon as you run iTunes again.

If you follow tt2's guidelines regarding Make a split library portable, you'll see that the preferred layout for an iTunes library (especially if stored on an external drive) looks like this:

My own master system, which uses this layout, has the complete library on an external drive (K:), so if I check the XML file the information right at the start of the file:

matches the iTunes Media folder location setting in Edit > Preferences > Advanced:

Similarly, the metadata within the XML file for a single track:

matches the location information shown using right-click > Get Info > File:

If you're seeing something different then I suspect that you're looking at an XML file that doesn't match the current library, and/or that your current library is actually the one on your system (C:) drive.

"The whole File->Library menu is tied to the local default library, not the selected library"

There is no difference between these - there is just one active library.  This is selected by iTunes on startup as follows:

• If you SHIFT-start iTunes, this will be the library that you select after clicking the Choose Library... option.
• If you start iTunes normally, it will use the library that was active the last time it was run unless that library file is unavailable (e.g., on a drive that has been disconnected or its drive letter has changed) - in this latter case iTunes will use the default library in C:\Users\username\Music\iTunes.

Note that double-clicking on a specific iTunes Library.itl file has no impact on these rules - iTunes will start and access the previously active library, even if that is different from the one you've double-clicked on.

Regarding http://imgur.com/NZRqvnT

This image suggests you are viewing a remote library which is somehow unnamed. What machine is it running on?

tt2

When you see a dropdown like this:

this indicates that Home Sharing is active.  The "This Computer" entry is always your current, active library.  Other entries are for shared libraries on other devices - usually other PCs running iTunes but may also be NAS or similar devices that offer "iTunes Server" functionality.  Therefore, when you select the second (unnamed) library from your dropdown you are then seeing a library on some other device - confirmed by the lack of file location information ... normally you'd expect to see the name of the remote library here:

but in your case you seem to have a shared library that is unnamed, so this field would be expected to be blank.

I would suggest that you identify where this remote library is located, then follow tt2's procedure in Make a split library portable to transfer this library to your external hard drive.  From the symptoms you've described I suspect that you may have inadvertently combined the media from your actual library (the one you're seeing as remote) with a "blank" iTunes Media.itl file from your new system.  It may also be worth looking through the "official" guidance on How to move your iTunes library to a new computer - Apple Support.

This Computer is the library that you select by shift-starting iTunes, and that my script will report on. When you select something else from that control it is another library on the network, hosted by an instance of iTunes running on a different computer.

tt2

"My machine, E:\iTunes\.  Standard Windows install on C:\.

Everything in my iTunes preferences is pointing to this file."

Common misconception, and one that's not really addressed by Apple's documentation.  The iTunes Media folder location setting in Edit > Preferences > Advanced is not used by iTunes to locate the current content of your library - that information is all contained within the iTunes database.  Rather, the iTunes Media folder location setting is used by the Consolidate Library function (which will move media from the locations specified in the database to that determined by the iTunes Media folder location setting), and when adding new media to the library, in combination with the Copy files to iTunes Media folder ... setting and the method used to add media:

Just to repeat from my previous response, when you see this type of dropdown:

everything listed after "This Computer" indicates a shared iTunes library on another device.  So, if you turn off sharing, these entries will disappear - indeed, if sharing is disabled or there are no shared libraries available on your local network, there will be no dropdown available:

" Lesson learned: just don't rename folders that are used by applications"

As far as iTunes is concerned, 100% correct - tt2's previously referenced user tip describes the operations that you can perform without affecting the integrity of your library.

"regardless of your iTunes Media Folder location, the local iTunes library itl will always be in ~/Music/iTunes/ folder."

No.  You can put the iTunes Library.itl file anywhere you want it to be.  Of the four systems I regularly use iTunes on, only one of these has a library on the system disc/default location - the others all have a well-formed library on an external drive, and don't even have a C:\Users\username\Music\iTunes folder.  The key to the "portable" layout is that you have one folder (typically named iTunes) that contains the iTunes Library.itl file and the iTunes Media folder.  As long as the relationship between the database file and media folder is preserved this structure can be anywhere on your system.  Also, there is no concept of a "local" iTunes database - much better to think of there being:

• the "active" library database - which can be anywhere you want it to be, and
• the "default" library database location, which will apply for any fresh install of iTunes or for the case where the active library from the last time iTunes was run cannot be found - this is C:\Users\username\Music\iTunes.