To construct by mental labor; to design and execute, or put together, in a manner involving the adaptation of forms of expression to ideas, or to the laws of harmony or proportion; as, to compose a sentence, a sermon, a symphony, or a picture.
To create, from your own imagination, a piece of music. Note: You cannot "Compose" someone else's song. If it isn't from your head entirely, you didn't compose it. See Also: Composer