Abstract
Amuzgo (Otomanguean: Mexico) has a large inventory of lexically arbitrary tonal inflection classes in person/number paradigms, where inflectional tones overwrite the root's lexical tone. In causatives, however, inflectional tones are predictable from phonological properties of the root, primarily lexical tone. The inertness of root inflection classes in causatives is argued to follow from cyclicity: once the causative Voice head triggers spell-out, lexical inflection-class specifications are no longer visible, and only phonological information can condition allomorphy in the outer domain of person/number agreement. The grammatical behaviour of inflectional tone thus reflects its structural morphosyntactic position, as distinct from its linear phonological one. I distinguish between several possible analyses of phonologically conditioned tonal-overwriting allomorphy, and propose that the Amuzgo case involves constraint-mediated competition among a priority-ranked list of allomorphs in the input, rather than creation of tonal allomorph candidates purely within the phonology or subcategorisation frames in the lexical representations of allomorphs.