I’ve found that, if your tags are meticulously correct, Plex won’t care about your folder/filename structure, as long as you use the “Plex Music” scanner (as opposed to the older “Plex Music Scanner” scanner). The following is not officially supported, as you just read 
, so this is at your own risk.
I ran kind of an extreme test case by copying a bunch of well-tagged music files from multiple artists into a single folder, and gave them generic filenames, so there were no clues in the folder/file names for Plex to rely on. Plex built the library nearly perfectly using the embedded tags.
There are some caveats, so pay close attention to the “Potential issues with embedded tags” section in the How-To I linked above. If classical music is important to you, be sure to check the “Classical Music” section as well.
