If you want it to stay shiny, get it relacquered.

Bigtiny, that machine is called an Ultrasonic machine. It has a very mild acid solution, and the sound waves create microscopic bubbles that explode and implode at very high temperatures very rapidly (it is called cavitation) Cavitation - Wikipedia, the free encyclopedia
A horn that is ultrasonically cleaned has to be scrubbed if it is really bad. Ultrasonics don't work well on large amounts of buildup.