Answer:
Tickle with your fingers and a song it will sing. Be careful, though, you may break a string. What is it?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
What is as light as a feather, but not even the strongest man on earth can't hold it for more than 1 c)minute?
What never gets any wetter no matter how hard it rains?
A king wears one on his head.
I build up castles. I tear down mountains. I make some men blind. I help others to see.