Ah, I understand a bit better now.
Have to disagree I'm afraid though. Musical talent is a gift from God and yes, it can be used to glorify God. It could also be used for Satan's purposes. But I do not think that a song which does not mention God is automatically the work of Satan. Perhaps it depends on who wrote it, in which case you would be right in your original point of the lyrics not being the only thing which makes it a Christian song.