I am a mom to a four year old kid.  There are ups and downs on being a mom.  Most of the time ups.  I see my little one happy and giddy all the time and that somehow rubs off on me.  I see her singing most of the time.  I think it is her way of coping boredom, or loneliness, or whatever it is she is feeling.  She does sometimes hums, simply hums when she was asked to do a chore.  She does "compose" songs too, and these are mostly the ones that makes me smile.  There never is a dull moment with her.