I tried to concatenate 2 MP3 files using the code below. I got a new file which I can play the first half of (complete first file), but the second half is silent. The length
Each MP3 file has a header at the beginning of the file containing the metadata of the song. At the very least you will have to remove that on the second file.
Here is a previous Stack Overflow question, How do I merge/join MP3 files with C#?.
Here's another link to Read MP3 Tag Information (ID3v1 and ID3v2), it might help you remove it.