Piano joke

Rico says it's an old one, but still good:

Mr. Opporknockity is a superb piano tuner. He has spent more than thirty years honing his craft and has made quite a reputation for himself.

He got a call from a guy who had just bought a new grand piano and requested Mr. Opporknockity to come and tune it. Mr. Opporknockity spent more than three hours tuning the grand piano to perfection, collected his fee, and left.

A couple of days later, the customer calls Mr. Opporknockity and informs him that the piano is not in tune.

The customer demands Mr. Opporknockity to return and re-tune the piano. To which Mr. Opporknockity replied, "My friend, you have missed out. Opporknockity tunes but once."