I have tried that exact procedure before (using an external card reader to copy the songs). Shortly after Xbox M+V had an update, which I duly applied. This trashed the database again. I will do the procedure again and see if it sticks this time, though I'm not hopeful.
While I appreciate all the suggestions on this issue, I suspect that WP8's music handling is simply too buggy at the moment to be suitable for my uses. I'm probably not your typical music listener as I'm a muso and add and delete stuff all the time from the music collection, mostly my recordings or those of friends. Music has worked flawlessly for me for years on my Xperia S with the Walkman app. If the music handling on WP8 is so fragile, and I have to jump through hoops and mutter various incantations to make it work, and then have the whole thing trashed by a simple app update, then I'm afraid WP8 is not for me at the moment. A shame - I really love the interface.
I hope this helps...
Following this steps I can fix the duplicates without resetting the phone (Ativ S) or formatting the SD
1) Move the duplicated albums mp3s (folders included) from the phone storage or SD to a folder on the PC.
2) Reformat their tags so that all the files use the same tags the same way.
3) Delete the files related to the duplicated albums in the Music/Albums folder in your Phone storage and, if needed, in your SD too
(keep in mind that when you remove an album file from the "Music/Albums" folder Windows Phone will slowly start to delete your mp3s in the source folder)
4) Copy your modified MP3S back to your SD
5) Wait some time for the phone to catalog the new files
Good and free mp3 tag editors:
Mp3tag -
www.mp3tag.de/en/download.html
Tag scanner -
www.xdlab.ru/en/index.htm
COMPILATIONS
For compilations, where songs should have different "song artist" tags although part of the same album, the
tag "album artist" must be the same in all the files and every track must have the "COMPILATION" tag set to "1"
(Mp3tag: "extended tags" in the right click menu on selected files - "Tag Scanner": just check "Part of compilation")
PARTIALLY MISSING ALBUM
If the music app finds a corrupted file in a folder While importing, usually it stops and moves to the next
folder, so, if you find that a album has been only partially imported, you should delete the broken file or
use a tool like "MP3 Diags" to repair it. (
mp3diags.sourceforge.net)