There's no better sound to lift the spirits than a child's laughter.
On my way to the library I saw a little boy of about five or six walking with his father–going to the same place. The father, walking by his son's side, put his hand upon the boy's head; the boy quickened his step, the father did the same, holding his hand in place on his son's head. The boy began giggling, walking faster, then running, the father kept up, hand in place, more hysterical giggles.
I walked into the library behind them with giggles in my heart.