Do you say Composed of or composed by?

"Composed of" is the correct phrase to use when describing the elements or ingredients that make up something. For example, "The band is composed of four members." or "The cake is composed of flour, sugar, eggs, and butter."

"Composed by" is used to refer to the person or people who created or wrote a piece of music or other work of art. For example, "The song was composed by Mozart." or "The painting was composed by Picasso."