Answer:
The man who invented it doesn't want it. The man who bought it doesn't need it. The man who needs it doesn't know it. What is it?
My voice is tender, my waist is slender and I'm often invited to play. Yet wherever I go, I must take my bow or else I have nothing to say.
What bird can lift the heaviest weight?
A shimmering field that reaches far. Yet it has no tracks, And is crossed without paths.
I work when I play and play when I work.
What is always coming but never arrives?