Problem Playing Chiptunes Containing VCR7 Sound

[Kyra Succubus]

I'm trying to play chiptunes from Lagrange point, a NES / Famicom game which uses the VRC7 sound chip. I've used six different players and get the same weirdness on each of them. In some parts of the songs, the volume will go to about 50% quieter, then return to normal. It does this repeatedly about every 20 seconds.

Do I need a plug-in for this, another player, etc.? Any help would be greatly appreciated. Thanks! :3