Hi, I had to recheck, and all of them are like this, some bit more recognizable (cuz they're louder) than others. But all the same.
I'm not sure it has to do with being from a different source more than the actual mechanic that puts the song around for the player to center. Like you either hear it from left or from right, but when you try to hear it from your front, it's switching from left to right (or otherway round). as if it's in 2D or something. and I believe it has to do with the 3D space and how your mechanic works. but overall a nice little game!