Ebonising: Ebonising is a process for darkening wood, giving it an appearance similar to ebony, hence the name.
It is particularly used for pianos and fine furniture including music boxes. Reference: Wikipedia
Ebonizing wood is not the same thing as simply coloring wood with ebony stain. When you ebonize wood, you’re causing a chemical reaction that makes the material turn black. The benefit to this process is opacity. When wood is stained you can sometimes see the grain through the stain. When wood is correctly ebonized it becomes pitch black, and you won’t be able to see grain through the color. Reference: Woodworker’s Guild of America
Below are some examples of music boxes made from ebonised wood.