More questions??
I think because most people have certain types of Music that makes them feel good whether it is because they enjoy playing it, listening to it, or dancing to it.
Now...I said "most" because some music is also sad and reminds people of other things or some music drives people crazy because they don't like it & it hurts their ears.
So...now in reference to your little one. As they get bigger, I'd play the music that makes them laugh or dance and then you can sit back and laugh at how cute they are!!