I think it's great the kids likes and get's into the music, but seriously? The volume? How sensitive a baby's hearing is! What ****** Parents. The kid wasn't going mellow or "feeling" the music in the end, he was having a seizure from his little ear drums exploding.
Exploiting your kids "talents" is fine, God know I think everything my boy does is great, but not if it's damaging. C'mon.
*edit*
After watching a couple more times, it doesn't seem the music is actually that loud. Especially in the back seat where the kid is.
I like how he looks at his fist like, "That song just took control of my body!"