Source : Webster's Revised Unabridged Dictionary (1913)

Composer \Com*pos"er\, n.
   1. One who composes; an author. Specifically, an author of a
      piece of music.

            If the thoughts of such authors have nothing in
            them, they at least . . . show an honest industry
            and a good intention in the composer. --Addison.

            His [Mozart's] most brilliant and solid glory is
            founded upon his talents as a composer. --Moore
                                                  (Encyc. of
                                                  Mus.).

   2. One who, or that which, quiets or calms; one who adjusts a
      difference.

            Sweet composers of the pensive soul.  --Gay.

Source : WordNet®

composer
     n : someone who composes music as a profession