It is not the music that is the problem. It is the hearing of it. The Bible tells you, faith comes by hearing (which is activity in your brain) and hearing by the word of God.
So, the activity in your brain is by something that in the beginning was with God and was God and nothing was made that was made without this activity then everything that has been made has been made by the word of God. That includes music.
The activity in your brain operates on a level that is conducive to your understanding. A child has little if no understanding of the activities that go on outside of their immediate environment. That is just the way the brain operates. The child's brain is like a sponge, soaking up everything it can to learn. That is the way the brain operates through the seeing, the hearing, the feeling, the tasting, the touching, but what is the chiefest sense?