Not all music files showing on Lumia 521 phone

[Sindrix]

I have music files on my SD card (transferred by connecting the phone to my laptop and using Windows Media Player on Windows 7) that I can see when I plug my phone into my laptop and use Explorer or the Windows Phone program, but when I go to my phone (while it's still connected to the laptop or not), not all of the music is showing. I downloaded the Pocket File Manager app to my phone to see if it could see the 'missing' files on my phone. It does see them and I can even tap the files to play them on my phone from the Pocket File Manager, but the music files still do not show up on the Music+Video app. I've double checked that these files are in the Music folder right alongside music files that DO show up on the Music+Video app. Anyone have an idea as to how I can fix this? I've tried resetting the phone, but not a factory reset.
Thanks!

 

[switch side method]

Try saving on phone. If it does it could be a dodgy SD card. What brand is the card?

 

[Sindrix]

Plain old MicroCenter.