Why does the music on my phone sound glitchy?

[AC Question]

I recently bought a Note 5 and added a bunch of music to it. When I listen to the music on my phone, it sounds glitchy with weird noises popping up here and there. When I listen to things like Spotify and Youtube on my phone, these issues don't occur. When I listen to the same files on my PC that I transferred to my phone, the issues don't occur.

 

[B. Diddy]

Welcome to Android Central! Where did you add these glitchy music files from? Downloaded from some music service, or some website?