I don’t really understand this

What is the central idea in this excerpt from act iii of romeo and juliet?

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.

How did duke ellington create a new musical style that grew out of the ragtime tradition?