Rere (Kordofanian, Sudan) has a complex system of grammatical tonal marking on verbs when both subject and object participants are expressed. There are verbs forms in which the position and segmental content of the participant markers are the same, but tone indicates whether the markers are interpreted as either subjects or objects. In addition, tone can distinguish the person/number of different subject markers. I will show how the verb is highly compositional in expressing multiple factors: tense/aspect/mood, lexical verb classes, subjects, objects and plurality. The expression of these categories, combined with tone spreading, results in several tonal minimal triplets, but a system that is highly regular.