The functions of Non-Final verbs and their aspectual categories in Northern Mao (Omotic) narrative

Northern Mao (Afroasiatic-Omotic) employs a set of non-final (medial/converb) verbs and aspectual morphology to distinguish events on the main storyline from background comment in narrative discourse. These verb-forms include same-subject (ss) and different-subject (ds) (medial verb-like) and temporally-integrated (ti) (converb-like) constructions in clause chains. While the ss and ds verbs move the storyline forward by marking sequences of main events, the ti verbs do not move the storyline forward; rather, they provide backgrounded commentary on main events. The ss and ds non-final verbs can take Perfect or Progressive aspect, which correlates with discourse function: Perfect divides discourse into major temporal sections and Progressive results in the possibility of temporal overlap (i.e. not part of the main storyline).