Features are standard in segmental analysis but have been less successfully applied to tone. Subtonal features have even been argued to be less satisfactory for the representation of African tone than tonal primitives such as H, M, L (Hyman 2010; Clements et al. 2010). I argue that the two-feature system of Yip (1980) and Pulleyblank (1986) offers a straightforward account of the tonology of Laal, an endangered, three-tone isolate of southern Chad – in particular properties of the Mid tone that are otherwise difficult to account for, namely the avoidance of complex patterns involving M, and a pervasive M-to-L lowering process, both straightforwardly analysed as subtonal assimilation. Other tonal operations in Laal are shown to involve full-tone behaviour, justifying a tone geometry à la Snider (1999, 2020) where subtonal features are linked to a Tonal Root Node, giving tones the ability to be either fully or partially active, just like segments.
