2. Summary of papers

The seeds of this issue were planted at the 2021 Princeton Phonology Forum (PɸF), whose focus was ‘tone and phonological theory’. Many of the talks at this workshop involved GT, and given the importance of this topic as a whole (as discussed in §1), this naturally led to the present issue. While some of the participants of that workshop have papers here, the two were formally separate and submissions were open to any and all interested parties.

Our issue is inevitably skewed towards Africa, in line with the characterisation that certain tonal regions of the world – in particular Asia – use tone primarily lexically rather than grammatically. Still, this issue involves a wealth of exemplification of GT from several languages families such as Mabia/Gur, Benue-Congo (especially its sub-branch Bantu), Kru and Nilotic in Africa, as well as Otomanguean in Mexico.

The first paper, by Hannah Sande, asks the general question ‘Is grammatical tone item-based or process-based?’ Morphology as item-based vs. process-based has been a long-standing debate in the morphological literature (Hockett Reference Hockett1954; Bermúdez-Otero Reference Bermúdez-Otero and Trommer2012), with certain frameworks, like the aforementioned Distributed Morphology, treating morphological operations as primarily item-based while others, such as Anderson’s (Reference Anderson1992) A-morphous Morphology, argue that morphology is better analysed as process-based.

In her article, Sande draws on case studies from a number of languages and develops a set of diagnostics to determine whether the GT alternations are best analysed as item-based, process-based or suppletive. These diagnostics include whether the GT has a consistent realisation across a paradigm, whether it is phonologically derivable, and whether it follows the general rules of the language’s phonology. If a case of GT meets all three criteria, it is best analysed as item-based; if it fails to meet any of the criteria, it is best analysed as suppletive; and finally, if it is phonologically derivable but is inconsistent in its realisation and outside of the regular bounds of the phonological grammar, then it is best analysed as process-based.

Sande goes on to show that item- and process-based morphology can in fact be unified in a single framework, Cophonologies by Phase (Sande Reference Sande2019; Sande et al. Reference Sande, Jenks and Inkelas2020). However, the distinction between items and processes remains relevant for how this framework captures GT. Item-based GT involves the addition of an underlying phonological form in the vocabulary item, process-based GT involves morpheme-specific constraint ranking and suppletive GT – such as the Chinese tone replacement case discussed in the article – requires lexical listing of allomorphs. While many excellent papers have analysed individual cases of GT, this paper highlights what GT can reveal about the architecture of the morphophonological grammar when diverse case studies are considered together.

Next are four papers focusing on GT patterns in particular languages. Most of the cases of GT involve tonological operations that express a morphosyntactic feature, but tone can interact with morphology in broader ways as well. Arto Anttila and Adams Bodomo’s paper, titled ‘Tone and morphological level ordering in Dagaare’ explores these latter interactions. In Dagaare (dga; Mabia/Gur, Ghana and Burkina Faso), tonal processes such as dissimilation, spreading and tonal absorption are sensitive to morphological level (stem level, word level, postlexical level) as well as syntactic category, and as such fit our working definition of GT as a grammatically restricted tonological pattern.

To expand, cross-linguistically nouns and verbs are subject to different constraint rankings and hence different tonal behaviour (Smith Reference Smith, van Oostendorp, Ewen, Hume and Rice2011). This situation is found in Dagaare. For instance, at the stem level, toneless syllables are filled in by H tone spreading in nouns, but by default L insertion in verbs, e.g. /tuu-ró/ $\to$ [túú-ró] ‘follow-ag’ (noun), but /tuu-ró/ $\to$ [tùù-ró] ‘follow-ipfv’ (verb). The key piece of evidence for level ordering in Dagaare comes from whether and how a sequence of two H tones is repaired. At the stem level, Meeussen’s Rule applies, dissimilating the second H tone to L. In contrast, at the word level, such as in compound formation, a downstep is inserted between the two H tones, and at the postlexical level, HH sequences are left unrepaired.

Anttila and Bodomo’s paper provides an example in which GT requires cyclicity in word formation: at most one downstep is permitted per word, and downstep derived at the stem level by contour tone simplification blocks the derivation of downstep at the word level, a familiar ‘inside-out’ effect. They couch their analysis in Stratal OT (Kiparsky Reference Kiparsky2000), where constraint rankings may differ depending upon stratum but also depending upon syntactic category, as in Cophonology Theory (Anttila Reference Anttila2002; Inkelas & Zoll Reference Inkelas and Zoll2007). In short, the authors demonstrate that ‘once morphology is properly understood phonology turns out to be simple’. GT thus proves to be an important tool in understanding morphology, phonology and the interface between the two components of grammar.

Next is Nadine Grimm’s paper ‘Exponence and the functional load of grammatical tone in Gyeli’. This examines the division of labour between tonal and segmental co-exponents of morphological categories, focusing on the intricate tone system of Gyeli (gyi; Bantu, Cameroon). GT is used almost exclusively in the marking of tense/aspect/mood and polarity on the verb and preverbal markers in Gyeli.

Grimm’s paper makes two main points. First, the more segmental material there is in a morpheme, the weaker the functional load of the tonal co-exponent of that morpheme. In other words, morphemes with both segmental and tonal co-exponents are characterised by one-sided redundancy: the segmental co-exponent would in most cases suffice to distinguish the morpheme (and the tonal information can be seen as redundant), whereas the tonal co-exponent on its own would not be sufficient (i.e. the segmental information cannot be considered redundant). Tone is thus morphologically informative and non-ambiguous only when it is the sole exponent of a morphological category.

The second point of the paper has to do with the relation between grammatical and lexical tones. Gyeli is a language where GT is ‘dominant’, following Rolle’s (Reference Rolle2018) usage of the term – that is, when confronted with a choice between the realisation of grammatical and lexical tones, the language always realises the former at the expense of the latter, which is overwritten. Interestingly, however, when there is room for both in a verb form (i.e. when there are enough tone-bearing units), both are realised. In other words, Gyeli strives to maintain both lexical and grammatical tones, and sacrifices lexical tone only when one of the two must go. GT in Gyeli is thus dominant only ‘under duress’, that is, as a last resort. This case exemplifies GT winning out over a root’s underlying lexical tone when they compete, a common situation in tone systems and one which contradicts the general finding with segmental patterns, in which a root’s phonological features are preserved over those of an affix (Urbanczyk Reference Urbanczyk, van Oostendorp, Ewen, Hume and Rice2011).

Bantu is one of the few families where there are both a critical mass of tone researchers and a substantial existing tone literature. It is therefore not surprising to find another Bantu-focused paper: Larry Hyman and Hildah Kemunto Nyamwaro’s paper on ‘Grammatical tone mapping in Ekegusii’. Indeed, their study here picks up where Bickmore’s (Reference Bickmore1997, Reference Bickmore1999) and Cammenga’s (Reference Cammenga2002) earlier studies on Ekegusii (guz) left off. Hyman & Kemunto Nyamwaro’s paper provides an extremely detailed empirical study of verbal GT, including a state-of-the-art description that works out the many conditioning factors governing the shape of individual GT patterns.

Their paper brings up several important theoretical issues. One is that in order to derive the Ekegusii tone mappings, global access to word-level morphological and phonological information is required. Thus, while the GT patterns themselves target the smaller prosodic stem domain, the conditioning factors need not be contained solely within this constituent. This finding is striking when put alongside other papers in this issue (in particular Yuni Kim’s; see below), which involve a more constrained cyclic model which lacks the power of such global calculations. Rather than viewing this simply as a contradiction, we see it as calling for a more nuanced theory which finely demarcates where we expect globality effects and where cyclicity effects.

Perhaps the most remarkable aspect of Ekegusii is yet another instance of what Rolle & Bickmore (Reference Rolle and Bickmore2022) descriptively refer to as ‘first–last tone harmony’, found infrequently but persistently across Bantu (Meeussen Reference Meeussen1967, Reference Meeussen1971; Nsuka Nkutsi Reference Nsuka Nkutsi1982; Schadeberg Reference Schadeberg1989; Roberts-Kohno Reference Roberts-Kohno2000, Reference Roberts-Kohno2014; Bickmore Reference Bickmore2007, Reference Bickmore2014; Hyman Reference Hyman2012; Jones & Freyer Reference Jones, Freyer, Clem, Jenks and Sande2019). Hyman & Kemunto Nyamwaro show that certain grammatical contexts in Ekegusii show ‘tonal agreement’ between the subject prefix, which appears at the left edge of the word, and the final inflectional vowel at the right edge. For example, in the ‘subject relative clause today past negative (Past1)’, if the subject prefix is lexically high-toned, then a grammatical high tone falls on the last suffix (e.g. ábanto bá-tá-á-súgum-á ‘people who didn’t push’). In contrast, if this subject prefix happens to be toneless, then the final suffix too must remain toneless and cannot host the grammatical tone (e.g. … o-tá-á-súgúm-a ‘…who didn’t push’). Rolle & Bickmore (Reference Rolle and Bickmore2022) interpret such globally sensitive patterns as suppletive allomorphy, and articulate the ramifications of this for linguistic theory with respect to morphological locality and directionality. Regardless of interpretation, non-local dependencies like this should be of major interest to linguists of several stripes (including the computationally minded, for whom first–last phonological harmony is said to be outside of what is possible in phonology; see Heinz & Idsardi Reference Heinz and Idsardi2013; Lai Reference Lai2015; Jardine Reference Jardine2020).

Lastly, Yuni Kim’s paper ‘Grammatical and lexical sources of allomorphy in Amuzgo inflectional tone’ takes us outside of Africa to examine the complex GT patterns in the Mexican language Amuzgo (azg). Amuzgo is part of the Otomanguean family, known for having some of the most complicated systems of inflectional tone (Palancar & Léonard Reference Palancar and Léonard2016), made especially challenging by the often large number of inflection classes whose membership appears to be mostly unpredictable. Amuzgo is no exception. Kim shows that transitive verbs in Amuzgo belong to up to 21 arbitrary inflection classes, defined by the distribution of replacive GT patterns in 1sg and 2sg forms. However, this irregularity levels out in derived causatives, where inflectional tone patterns become predictable based on the lexical tone of the verb root.

Kim accounts for this discrepancy in behaviour by appealing to cyclic spell-out: morphosyntax spells out in chunks when a phase head is reached, and morpho-lexical features are checked off in the process, so that they are no longer active or visible at later cycles (Bobaljik Reference Bobaljik2000). Causatives contain a Voice head, which triggers spell-out, and so by the time person inflection is reached, the verb’s inflection class features are no longer active; thus, allomorphy can be sensitive to phonological form alone. Non-causatives, on the other hand, contain no such phase head, and so tone marking person can be sensitive to inflection class. Kim’s work thus adds to the growing number of case studies in which GT provides crucial evidence for a cyclic model of morphosyntax (see also McPherson & Heath Reference McPherson and Heath2016; McPherson Reference McPherson2019; Sande Reference Sande2019; Sande et al. Reference Sande, Jenks and Inkelas2020).

Kim analyses the replacive nature of Amuzgo GT with a combination of allomorph listing and cophonologies. Essentially, every input contains both the root’s and any affix’s lexical tones, along with a list of candidate allomorphs with each of Amuzgo’s five possible inflectional tones. These allomorphs are listed in a preferred order, with a constraint Priority assigning an increasing number of violations the farther down the priority list a particular allomorph is. Slightly different constraint sets for 1sg and 2sg inflection account for tonal differences between these two forms. Viewed in terms of Sande’s diagnostics, Amuzgo GT appears to be suppletive. It is not phonologically consistent across the paradigm; it is not easily phonologically derivable (as Kim shows in her §4.2); and it does not follow the general phonology of the language. Nevertheless, the choice between listed suppletive allomorphs can be phonologically conditioned. Thus, Kim’s analysis of Amuzgo GT elucidates not only the larger architecture of morphosyntax but also the details of how phonology and morphology interact to decide upon surface allomorphs.