Mp3Tag is really weak compared to The GodFather :
http://users.otenet.gr/~jtcliper/tgf/Many formats are supported and the interface is marvellous (as feature-full than colorful).
You can update files one by one, or by folders.
You can make it guess tag values from file names, folder names, or from the online database you prefer.
There's also a playlist editor and a player to listen music while your updating your tags (or to convert between formats).
And a full-featured "library", a database of all your songs/tags to organize them the way you want without messing your folder structure (uh, oh, i forgot, it can also create this folder structure and move/copy/rename your files).
And if that's not enough (i would hardly beleive that), you can make little scripts for any of the above functions (errm.. not the "library" of course).
You just can't live without TGF's green parrot icon on your desktop...
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