Who wrote the music for the nutcracker?

You know what i love about this sight when ask a dumb question it is immediately answered but when i ask a real question it takes hours to get answered

To make an etching the artist first coats the entire printing plate with an acid-resistant substance called a made from beeswax, asphalt, and other material. the artist then draws on the coated plate with an etching needle exposing the metal. next the plate is dipped in the plate is removed, the waxy coating removed, and the plate is cleaned, inked and printed.

For the difference command to work, what needs to happen?