Consider Making Your Library Files Read-only
After tagging your library files as you want them tagged, consider making them read-only. If someone removes that attribute on certain files, you can easily detect the change through Windows Search by searching against the read-only and archive attributes:
attributes:<>33
32 is the Archive flag plus 1 for Read-only.
You can also display file attributes in explorer as a column. In that column RA indicates read-only. If a file in the column does not show an R, then that file is not read-only.
Attribute query details are found here:
https://social.technet.microsoft.com/Forums/en-US/fede1d8e-130c-4e69-9b2b-48cf3f904c43/windows-search-advanced-query-syntax-aqs-and-file-attributes?forum=w7itproui
You might also want to warn library users against removing the read-only attribute from the library originals. If they really need to add their own tags, then they should make local working copies of the files.
UPDATE: additional (more complete) references kindly provided by LyricsLover in the German discussions: Attrib - Edit file attributes - Windows CMD - SS64.com