A composer is a person who creates or writes music, which can be vocal music (for a singer or choir), instrumental music (e.g., for solo piano, string quartet, wind quintet or orchestra) or music which combines both instruments and voices (e.g., opera or art song, which is a singer accompanied by a pianist). The core meaning of the term refers to individuals who have contributed to the tradition of Western classical music through creation of works expressed in written musical notation (e.g., sheet music scores). (source)