Hi Hamsen, the performance or the service of Mp3tag is not so much tagging music files, but to provide a straight and useful user interface for it.
A special service of Mp3tag is dealing with different Tag versions and types of music files.
Not to forget all the logic behind the curtain.
There are numerous ready made programs and programming scripts written in different programming languages spread all over the world, which can tag your music files, including some specimens that come along as a pure DLL file, perhaps there exist also COM objects, maybe .NET assemblies too, even in the freeware area.
An Internet research can be helpful, possibly starting at Wikipedia.
Sometimes I dream about having access to my music files via a COM object that relies on the expertise of Mp3tag.
You need to take into account that Mp3tag is not a "simple" console program that just once can be transformed into a DLL to be used from any programming language aside.