Is grammatical tone item-based or process-based?

This article considers the question of what constitutes item-based morphology, with a specific look at grammatical tone. Numerous case studies of grammatical tone are examined in light of the debate on whether morphology is item-based or process-based. In each case, tonal alternations are an exponent, sometimes the sole exponent, of some grammatical feature. Two of the case studies are examples of grammatical tone that can straightforwardly be analysed as involving concatenated morphophonological forms; however, in other cases, the grammatical tone cannot be reduced to the concatenation of a tonal affix or phonological feature with some stem. The latter type cannot straightforwardly be analysed as item-based, but if still phonologically predictable and productive, is not satisfactorily analysed as suppletive. This article suggests a set of diagnostics that can be used to determine whether a given phenomenon is best analysed as item-based, process-based or suppletive. Then, an analysis is presented in Cophonologies by Phase (CbP), where morphosyntactic features can be mapped not only to underlying phonological items, but also to morpheme-specific constraint weight adjustments. CbP allows for what may have been traditionally called item-based and process-based morphology to co-exist in a single framework.