Writer, author, composer can all denote a person who gives expression to his ideas or feelings, but they are not as a rule synonyms.
Writer is a comprehensive term applied to someone whose occupation or chief employment is that of expressing something in words, especially for others to read. As an occupational designation, it implies that one’s profession is writing for publication, and it covers such persons as novelists, essayists, dramatists, editors, and journalists.
Author in its comprehensive sense (see under MAKER ) is applicable to a producer or source (as of a work of art), but it can be applied specifically to a person who has written for publication. It differs from writer in placing less stress upon the profession and more upon the fact of having written and published something (as a book or an article under one’s own name or a pen name).
Author in this sense, too, implies an originator or source and is distinguished from reviser , adapter, editor , or dramatizer .
Composer , like author , may be used generally and specifically. But because it emphasizes the bringing together of a number of things so as to form a whole (a composition), it is applied most frequently to those expressions of ideas or feelings achieved by bringing together musical tones, words, colors, or shapes so as to form an artistic pattern.
It is the specific term for the author of a musical composition, but, although this is its commonest application, it is also applicable to poets, painters, designers, and others when composition rather than creation or representation is the end.