Problem: artists messed up

Hi guys. My friend has a problem. He had a Samsung MP4 player and everything was fine because he just used to import folders with songs into it as a USB device. With iTunes on his iPod Touch, he's having problems. As you can see, iTunes duplicates the same artists in different catalogs. Why? How does it work? How can he fix? Thanks

Here's two examples:

https://www.dropbox.com/sh/b7hbpgpeutzxvif/AADj_khgxP_AJNFzmi3k5jH6a?dl=0