"My brother is a composer (at somewhere or a certain kind of)." cf: (Nom) (My brother is a composer) vs. (Ess) (My brother works/acts as a composer (somewhere)) ' "composer" → ' "state of being a composer (the given time is the present)" Example: "My brother is a composer in an orchestra". Example: "As a composer my brother is unique".
"My brother is a composer (at somewhere or a certain kind of)." cf: (Nom) (My brother is a composer) vs (Ess) (My brother works/acts as a composer (somewhere)) ' "composer" → ' "state of being a composer (the given time is the present)" Example: "My brother is a composer in an orchestra". Example "As a composer my brother is unique"