When you sing God laughs with joy

Tonight William was singing softly as we put him to bed.  Peaceful and happy this nice evening.  When he sings I like to say to him: 

"William when you sing God laughs with joy"

Sometimes when I say that this eyes open up amazed and he sings louder.  I think it is his way of praying now.  Sometimes he cries when he sings, almost a wail, at others, he laughs, then there are the days like tonight, when his singing is peaceful and simply lovely.