2.1 Reductive coalescence

A prototypical example of reductive coalescence involves an alternation in which a sequence of two adjacent underlying segments surfaces as a single output segment which has some properties of each of the input sources. This is most commonly seen in hiatus resolution. In languages such as Xhosa and Chumburung in (2), a sequence of vowels of different quality is simplified to a single vowel, which has the backness of one of the inputs, but the height or ATR specification of the other. In Xhosa, coalescence applies to resolve vowel hiatus across various morpheme boundaries, for example between the possessive marker /ɓa-/ and the vocalic class prefix of a noun it attaches to, or between a noun and the locative suffix /-ini/ (all Xhosa data in the paper are from Pahl et al. Reference Pahl, Pienaar and Ndungane1989, Mini & Tshabe Reference Mini and Tshabe2003 or Tshabe & Shoba Reference Tshabe and Shoba2006). Input /a-i/ and /a-u/ sequences formed across these boundaries are realised as output [e] and [o] respectively. Thus the resulting mid vowels are [―high], like the input /a/, but their values for [back] and [round] correspond to the second vowel in the input sequence. In Chumburung, where hiatus resolution affects vowel sequences spanning word boundaries, the resulting vowel has the [low], [back] and [round] specification of the second vowel in the underlying sequence, but may have the [ATR] and [high] values of the first one (all Chumburung data are from Snider (Reference Snider1989, Reference Snider2018) or from Keith Snider (personal communication)).Footnote ²

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While reductive coalescence is often discussed in the context of hiatus resolution, it can also affect consonant clusters and combinations of vowels and consonants. The latter can be observed in Chumburung. When the first vowel in an underlying sequence is rounded, it fuses with the preceding consonant, yielding a labialised segment, as in /átɔ́ àsá/ → [àtʷàsá] ‘three things’ (Snider Reference Snider2018: 103).

A classic example of coalescence affecting sequences of consonants is ‘nasal substitution’ in Indonesian (De Guzman Reference De Guzman1978, Pater Reference Pater, Kager, van der Hulst and Zonneveld1999, Reference Pater and Lombardi2001, Blust Reference Blust2004), where the final velar nasal in the active voice prefix /məŋ-/ seems to fuse with a stem-initial voiceless stop or fricative, creating a nasal with the place of articulation of the input obstruent, as in (3) (Lapoliwa Reference Lapoliwa1981: 106–107, Sneddon et al. Reference Sneddon, Adelaar, Djenar and Ewing2010).

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A less prototypical type of reductive coalescence includes non-local patterns, such as the one described for Chaha (Banksira Reference Banksira2013), where the exponent of the impersonal subject suffix, realised as [w] when it occurs between vowels, as in (4a), fuses with the nearest preceding labial or velar segment when it is underlyingly preceded by a consonant, skipping intervening vowels and coronal consonants, as in (b).

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Finally, reductive coalescence includes alternations in which the number of segments is reduced without loss of featural content, as could be argued for Polish, where a stem-final dental stop (e.g. in [studɛnt] ‘student’) and an alveolar fricative of the denominal adjectivising suffix /-sk/ (e.g. [xwɔp-skʲ-i] ‘peasant (adj)’; cf. [xwɔp] ‘peasant’) are simplified to a single affricate ([studɛn«ʦ»kʲ-i] ‘student (adj)’; Gussmann Reference Gussmann2007: 154).Footnote ³ It has also been argued that some apparent cases of segment deletion should instead be analysed as vacuous coalescence, whereby the fused output retains all the features of only one of the input segments. Vacuous coalescence has also been claimed to encompass cases of morphological haplology (Lawrence Reference Lawrence and Haraguchi1997, de Lacy Reference de Lacy, de Lacy and Nowak2000), in which an affix is absent in the context of a featurally identical or near-identical string.Footnote ⁴

The exact nature of reductive coalescence alternations has been the subject of considerable debate in phonological literature. One prominent claim is that coalescence is the effect of the interaction of two independent processes of assimilation and deletion, where deletion removes the source of the spreading feature, rendering assimilation ‘opaque’ (Kiparsky Reference Kiparsky and Dingwall1971, Reference Kiparsky and Fujimura1973). For example, Herbert (Reference Herbert1986: 252) analyses Austronesian nasal substitution as regressive nasal place assimilation followed by deletion of the triggering obstruent. A different analysis of Indonesian nasal substitution is suggested by McCarthy (Reference McCarthy2007: 88–91), who argues that it could be viewed as the opaque interaction of progressive nasality assimilation and deletion of coda nasals. Similarly, for hiatus resolution in both Xhosa (Aoki Reference Aoki1974) and Chumburung (Snider Reference Snider1989), analyses have been proposed in which a lowering rule affecting the second vowel in a sequence is made opaque by a later rule deleting the vowel that triggers lowering.

Other authors, however, have questioned whether this approach is feasible for all cases of reductive coalescence, citing typological and language-internal arguments. In this article, I follow Awobuluyi (Reference Awobuluyi1987) and Pater (Reference Pater, Kager, van der Hulst and Zonneveld1999) in assuming that while some patterns of coalescence, which I refer to as assimilatory, can be analysed as opaque interaction of assimilation and deletion, others (which I call compensatory) cannot. Below, I outline the diagnostics that have been proposed to differentiate between the two.

2.2 Non-reductive coalescence

In addition to examples of coalescence similar to those described in the previous section, the literature contains reference to a different kind of fusion process, affecting adjacent identical or partially identical segments. This type of coalescence, which I refer to as non-reductive, often cannot be identified by looking at the phonetic realisation of the string, because the output contains the same number of segments as the input, with the same featural and tonal specifications. What distinguishes segments that have undergone non-reductive coalescence from those that have not is their phonological behaviour, with segments that have undergone the process behaving as a single unit for the purposes of other processes. This has been argued for adjacent tones and adjacent identical consonants.

A classic example from the domain of tone is offered by Myers (Reference Myers1987, Reference Myers1997) in his analysis of tonal patterns in the Zezuru dialect of Shona. Myers argues that the effect of Meeussen's Rule (Goldsmith Reference Goldsmith, Aronoff and Oerhle1984) in the dialect is best explained by the assumption that the process is preceded by fusion of adjacent underlying high tones into a single high tone. In Zezuru Shona, the application of Meeussen's Rule at the word level lowers a span of adjacent high-toned syllables, even when they are heteromorphemic, as in (8). (All Shona data in the paper are from Myers (Reference Myers1987, Reference Myers1997). The language has two level tones – high (ˊ) and low ( ) – and no contrastive contour tones. Square brackets indicate the boundaries of the constituents juxtaposed at the word stratum.)

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Myers (Reference Myers1997) provides evidence to show that the process is driven by a syllable-mediated OCP constraint, which penalises adjacent high tones associated to adjacent syllables. This means that in the examples in (8) it should be enough to lower the tone on just one of the syllables, giving *[í] [bangá], for example, rather than [í] [banga]. Myers explains the fact that the entire tonal span is affected by arguing that the high tones fused at a previous stratum. Thus, at the point at which Meeussen's Rule applies, it affects a single tonal element. Since this element is now associated to more than one syllable, the process has the effect of lowering an entire span.

Non-reductive coalescence has also been posited to explain a number of nearly universal characteristics of morpheme-internal geminates, such as geminate integrity and full alterability. Geminate integrity (Leben Reference Leben1980, Steriade Reference Steriade1982, Hayes Reference Hayes1986b, Schein & Steriade Reference Schein and Steriade1986) refers to the observation that epenthesis processes that break up consonant clusters tend not to affect geminate consonants, while full alterability (Keer Reference Keer1999) concerns the fact that feature-changing processes targeting structures present in a geminate in some lefthand environment tend to affect the entire geminate. Both facts can be explained if geminates are represented as a single melody associated to two timing units. This representation can be arrived at by coalescence of adjacent identical consonants.

3.1 Basic principles of Autosegmental Coloured Containment Theory

3.2 Compensatory reductive coalescence

Recall that in reductive coalescence two underlying segments are simplified to one, which typically bears features from each of the input segments. I analyse this as underparsing of one of the root nodes, coupled with the reassociation of a feature or features from the underlying host to a neighbouring one; cf. (10a). In compensatory reductive coalescence, underparsing and reassociation seem inextricably linked, with no evidence for independent processes of deletion and assimilation whose interaction could produce the effect of fusion.

I propose that compensatory coalescence should be analysed as a subclass of a broader phenomenon of autosegmental stability under deletion. Stability effects, first discussed by Goldsmith (Reference Goldsmith1976) as an argument for autosegmental representations, refer to situations in which elements on some tier or tiers are deleted, but elements on lower tiers to which the deleted elements were associated are preserved. Although most commonly discussed in reference to tonal patterns, stability effects have been argued to extend to other autosegmental tiers, including the skeletal or moraic tier (Hayes Reference Hayes1989) and featural tiers (e.g. Mascaró Reference Mascaró, Wetzels and Sezer1985, Prunet Reference Prunet1986, Wetzels Reference Wetzels1995, Vaux Reference Vaux1998). This idea was extended to patterns of reductive coalescence in early OT analyses of hiatus resolution (Casali Reference Casali1996) and patterns of consonantal coalescence in Navajo and Chipewyan (Causley Reference Causley1997). This section presents an ACC adaptation of an analysis of Xhosa vowel coalescence outlined by Casali (Reference Casali1996) as a means to familiarise the readers with the notations and conventions used in the article, and to serve as a basis for later comparison with the analysis of assimilatory coalescence in §3.3 and for further theoretical discussion in §4.

In reductive coalescence, underparsing, resulting in a reduction in the number of phonetically realised host nodes, is the effect of a high-ranked markedness constraint satisfied by a candidate in which an underlying root node fails to be integrated into higher prosodic structure. The identity of the markedness constraint depends on the segments forming the penalised structure; for all alternations discussed here, the driver can be assumed to be a sequential or syllable markedness constraint. For hiatus resolution, as in Xhosa and Chumburung in (2), the constraint is *Hiatus in (14) (adapted from Pulleyblank Reference Pulleyblank and Bobda2008: 127), which prohibits adjacent vowels. The constraint is a phonetic clone, indicated by underlining. The phrase ‘in P’ in the definition refers to P-structure, i.e. the overt part of an output candidate.

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To block the prosodification of one of the input root nodes, the markedness constraint has to outrank faithfulness constraints that are violated by underparsing. Here, the relevant constraint is Max(•) in (15a), which penalises covert underlying material (here, coloured root nodes that are not properly integrated).Footnote ⁶

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Max(•) and other faithfulness constraints violated by underparsing have to be outranked by faithfulness and markedness constraints that militate against other hiatus-resolution strategies, such as consonant epenthesis, which is prohibited by Dep(•) in (15b). Additionally, the driver has to be supplemented by constraints that govern the directionality of deletion (i.e. whether the first or the second segment in a sequence is not prosodified; for example, underparsing the leftmost rather than the rightmost H node in (10a)). Casali (Reference Casali1996: 27, Reference Casali1997: 508) proposes an account in which the deletion of the first vowel in a sequence spanning the root–suffix boundary is favoured by a positional faithfulness constraint requiring the preservation of morpheme-initial segments. An ACC version of this constraint protects the leftmost element in a span of nodes with the same morphological colour, as in (16).Footnote ⁷

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The interaction of the constraints discussed above can be illustrated with a set of Xhosa forms in which hiatus is resolved by deletion, rather than coalescence, such as those in (17), where the high front stem-final vowel is deleted before the initial vowel of the locative suffix /-ini/.

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The tableau in (18) shows the evaluation of the word /i-lali-ini/ → [elalini] ‘village (loc)’.

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If all parts of the input are fully integrated into higher prosodic structure, as in candidate (a), *Hiatus is fatally violated. The winning candidate, (b), avoids this violation by leaving the stem-final root node unsyllabified. This results in the non-realisation of the first vowel in the sequence and the violation of Max(•). Candidates that involve other ways of circumventing the violation of *Hiatus are either harmonically bounded, like (c), in which the failure to integrate the suffix-initial root node incurs a superfluous violation of the positional faithfulness constraint Max(_M[•), or fall foul of higher-ranked constraints, like (d), where splitting the vowel sequence with an epenthetic consonant violates Dep(•).

In coalescence alternations, the non-pronunciation of a root node is accompanied by the reassociation of some features underlyingly dominated by that root node onto a different, phonetically realised, host. In Xhosa hiatus resolution, this feature is [―high]. In an OT analysis that treats the reassociation as a stability effect, the operation is driven by a high-ranked constraint mandating that some underlying node be realised phonetically. Here, the relevant constraint is Max[―high], whose ACC definition is given in (19).

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Compensatory coalescence arises when separate Max constraints require the preservation of two disconnected nodes that form part of (or are dominated by) the same marked structure. Repairing the structure by deleting one segment would violate some Max[F] constraint; deleting another segment would violate another feature-preservation constraint (Max[G]) or a positional Max constraint. Reassociating the feature protected by Max[F] from its host to a node protected by positional faithfulness (or to a node dominating another protected feature) and deleting the host is a win–win strategy that makes it possible to retain both protected nodes while repairing the marked structure. This is shown in (20) for the Xhosa word /i|’ala-ini/ → [e|’aleni] ‘side (loc)’.

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As in (18), *Hiatus is fatally violated by the segmentally faithful candidate, (a). The newly introduced featural faithfulness constraint Max[―high] eliminates candidate (b), in which the first vowel in the hiatus is deleted.Footnote ⁸ Deleting the suffix-initial high vowel, as in candidate (c), incurs a fatal violation of Max(_M[•). The coalescence candidate, (d), is optimal, because it retains both the suffix-initial vowel and the [―high] feature, at the cost of violating low-ranked Max(•) and Max[+high].

The same type of analysis can be applied to other patterns of compensatory coalescence, such as nasal substitution in Indonesian (cf. (3)), where Max[+nas] would drive the reassociation subcomponent. Non-local coalescence patterns, such as the one in Chaha in (4), where the back glide fuses with the nearest preceding labial or velar segment, are also amenable to an analysis in terms of feature stability, here driven by Max[+round]. Long-distance reassociation can be enforced by a segmental markedness constraint which prevents certain combinations of features. Since the [+round] feature in Chaha docks onto velars or labials, the relevant constraint is *[cor]ʷ in (21), which penalises labialised coronals.

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The fact that a feature can reassociate onto a non-adjacent host raises the question of how the locality of reassociation should be constrained, not only in Chaha, where the feature lands on a suitable segment closest to the underlying host, but also in languages where coalescence is fully local, with reassociation only allowed between underlyingly adjacent segments. To this end, ACC has two constraint families at its disposal, NoSkipping in (22a), which penalises skipping nodes in association, and NoCrossing in (22b), which penalises crossing association lines (cf. Trommer Reference Trommer2011: 54).

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The directionality of reassociation is governed by a class of constraints that penalise epenthetic association to nodes preceding or following an underlyingly associated node, as in (23).

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The effect of these constraints is shown in (24) for Chaha /gəfər-w-p-a-m/ → [gəfʷərpam] ‘one released to her detriment’ (Banksira Reference Banksira2000: 29). I assume that the deletion subcomponent of coalescence is driven by constraints on syllable structure, collectively referred to as Syll: *Complex, penalising complex syllable margins, and *Coda(G), violated by glides in the coda position. To save space, (24) and the following tableaux only include detailed phonological representations of the relevant segments, and the specifications for some features are shown above the root nodes that dominate them. All prosodic structure above the level of the root node is omitted. A greyed-out node on the highest tier shown should be taken to be unintegrated into any higher structure, by analogy with the greyed-out root nodes in (18) and (20).

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The fully prosodified candidate, (a), violates a constraint governing syllable structure (depending on the syllabification, either *Complex or *Coda(G)), while candidate (b), in which the underlying glide is left unsyllabified, falls foul of the Max constraint protecting the feature [+round]. In the remaining candidates, the feature is rescued by reassociation to a different segment in the word. In candidates (c) and (d), the reassociation is local, leading to violation of high-ranked constraints controlling the directionality of reassociation, (c), or the quality of segments in the surface inventory, (d). The directionality constraint is a general clone, which assesses the entire output form. Consequently, it is violated by the rightward spreading, even though one of the association lines involved in the marked structure is not realised phonetically. The same is true of the NoSkipping constraint, which ensures that the feature [+round] lands on the rightmost non-coronal consonant that underlyingly precedes the source of the feature, (e), rather than one further away, (f).Footnote ⁹ Even though the overt subparts of the two candidates do not include a [+round] feature shared between two non-adjacent root nodes, this configuration is covertly present in each candidate, and incurs as many violations of NoSkipping as there are root nodes separating the original and the new host.

3.3 Assimilatory reductive coalescence

Constraints from the Max[F] family make it possible to account for most examples of reductive coalescence, and could in principle be used to derive patterns of assimilatory coalescence, such as those in Chumburung in (2b) and Modern Greek in (5a.i). Nevertheless, as pointed out in §2.1.1, viewing coalescence as the result of the opaque interaction of assimilation and deletion does seem warranted in some cases. Treating such patterns as cases of feature stability has a drawback, in that it fails to express the relationship between the quality of the feature preserved in coalescence and the quality of the feature that spreads in an independently observed process of assimilation.

ACC offers a way to link the two. Recall that in this framework, covert material, which remains unpronounced but is nevertheless present in the output, can affect the shape of overt material via general markedness constraints, i.e. clones of independently motivated phonetic constraints that assess the entire structure, not just its properly integrated subpart. This makes it possible to treat assimilatory coalescence as a case of the overapplication of assimilation, whereby the process is driven by a constraint that demands spreading of a given feature irrespective of whether its host is properly integrated (and hence phonetically realised). In ACC, opaquely driven overapplication opacity is effected by general clones of positive markedness constraints, which penalise structures lacking a certain property, and can therefore drive its insertion or spreading.

Under the assumption that postnasal voicing in Modern Greek is an NC̥ effect, the (opaque) spreading of [+voice] can be driven by a positive reformulation of Pater's (Reference Pater, Kager, van der Hulst and Zonneveld1999) *NC̥ constraint (which assigns a violation for every nasal stop followed by a voiceless obstruent) as a constraint of the Share family (McCarthy Reference McCarthy, Goldsmith, Hume and Leo Wetzels2010: 200, Trommer Reference Trommer2011: 230), which penalises adjacent segments in a nasal–obstruent sequence that are not associated to the same [+voice] node, as in (25).Footnote ¹⁰

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I follow Arvaniti (Reference Arvaniti1999a) in assuming that Modern Greek deletion is driven by *Coda. As shown in the evaluation of the relevant fragment of /tin ˈkɐpɐ/ → [ti ˈgɐpɐ] in (26), the constraints mentioned above are sufficient to account for the voicing + deletion pattern in Modern Greek.Footnote ¹¹

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In (26), the faithful candidate, (a), violates two high-ranked markedness constraints, Share[+vd]_NC and *Coda. In candidate (b), voicing spreads from the nasal onto the following stop, which satisfies Share[+vd]_NC. However, the coda nasal still violates *Coda. In (c), the nasal is not prosodified. This leads to *Coda being satisfied, but not Share[+vd]_NC, since the latter constraint assesses the entire output structure, which still contains a sequence of root nodes that do not share the [+voice] feature. The optimal output is candidate (d), in which voicing spreads from the covert nasal.

The same kind of analysis, with the general clone of a positive markedness constraint driving the spreading of a feature from a phonetically unrealised source, can be applied to vowel coalescence in Chumburung in (2b). In addition to the presence of independently motivated processes of vowel deletion in (6b) and spreading of the features [+ATR] and [―high] in (6a), the language provides theory-internal evidence against treating the reassociation of [+ATR] in terms of feature stability driven by a Max[+ATR] constraint. First, the two assimilatory processes illustrated in (6a) interact in an opaque manner: although progressive ATR harmony does not normally affect [―high] vowels (e.g. [bùnì bàsà] ‘butterfly's needle’, [bùnì bɔ̀tɪ́] ‘butterfly's sack’; Snider Reference Snider2018: 122–123), it does apply to mid vowels derived from high ones by the lowering process, as evidenced by the first example in (6a.ii). As explained above, an ACC account of this type of overapplication requires the constraint driving progressive ATR harmony to be a positive general clone. If this is the case, then the process is predicted to overapply not only when the target vowel is lowered, but also when the source vowel is not realised phonetically, producing the effect of coalescence, as in the phrase /ìwú ɪ̀sá/ → [ìwí↓sá] ‘three thorns’. Under these circumstances, adding a Max[+ATR] constraint to the evaluation has no effect on the outcome. A further potential problem for an ATR-stability analysis (noted by Casali Reference Casali1990: 337 in his discussion of possible [+round] stability in Nawuri) is that, due to a word-level harmony process, all vowels within a Chumburung word (save for syllable-final low vowels) have the same [ATR] value. If word-level harmony is understood as sharing a single [ATR] feature, then deleting the last vowel in a polysyllabic word does not lead to a violation of Max[+ATR], and reassociation is not expected. Since in Chumburung, [+ATR] reassociates even when the first word is polysyllabic (as in /ìpésí ɪ̀sá/ → [ìpésí↓sá] ‘three brooms’; Keith Snider personal communication), an analysis that treats [+ATR] reassociation as a genuine case of assimilatory coalescence seems more appropriate.

3.4 Excursus: vacuous coalescence

As noted in §2.1, some instances of apparent segmental deletion have been argued to involve vacuous coalescence instead. In some cases, the deletion analysis is a by-product of the correspondence-theoretic constraint ranking. As pointed out by Wheeler (Reference Wheeler2005a), languages in which sequences of segments are simplified in the same context by either coalescence or deletion, depending on the quality of the segments involved, require that both types of reduction be treated as a two-to-one mapping. This is because a correspondence-based analysis necessitates a ranking in which any constraint violated by a coalescence candidate, such as Uniformity, is ranked lower than constraints militating against other repairs, including Max, which penalises segmental deletion. In deletion contexts, this ranking will eliminate candidates in which one input segment has no output correspondents, in favour of coalescence candidates in which an output segment corresponds to two inputs, but happens to preserve all features of only one of them.

As illustrated by the analysis of Xhosa hiatus resolution in §3.2, this ‘once coalescence, always coalescence’ interpretation of segment-reduction patterns is not necessary in the proposed account. In words in which the first vowel in hiatus is [+high], the optimal candidate is one in which one root node, together with all the features it dominates, remains unpronounced, as in (18). It is only when the first vowel in hiatus is [―high] that underparsing of the root node is accompanied by reassociation of the protected feature to a neighbouring host, producing the effect of coalescence, as in (20). Nevertheless, ACC still makes it possible to describe a kind of vacuous coalescence involving vacuous spreading, where the reassociating feature lands on a segment dominating a feature with an identical value. In contrast to the correspondence-based analysis, however, such a candidate does not have to be the winner, as it can be eliminated by a high-ranked constraint against root nodes dominating identical features.

In addition to analyses involving vacuous coalescence as a ‘by-product’, arguments have been put forward for analysing some segment–zero alternations as cases of crucial vacuous coalescence, on the basis of language-internal or typological evidence against deletion accounts. One case in point is the reduction of syllable-final homorganic clusters in (Central) Catalan, as in [punˈt-ɛt] ‘bridge (dim)’ vs. [pɔn] ‘bridge’ (Wheeler Reference Wheeler2005a, Reference Wheeler2005b: 221). Baković (Reference Baković2017) argues that treating this pattern as coalescence makes it possible to uphold his theory of antigemination (Baković Reference Baković2005), which states that avoidance of ‘sufficiently similar’ adjacent consonants is the result of the interaction of two constraints: NoGem, a strict antigemination constraint against fully identical adjacent consonants, and some constraint enforcing assimilation of the features ignored in the determination of identity (e.g. Agree or Share). Catalan homorganic cluster reduction constitutes a prima facie counterexample to this theory, since it incorrectly predicts that all but place features should assimilate in the language. Baković (Reference Baković2017) points out that this prediction is not made if the Catalan pattern is treated as coalescence driven by a constraint against complex codas. In this case, the reduction is not the result of avoidance of segments that are similar enough. Rather, all sequences of tautosyllabic segments are disfavoured, but only those that have the same place of articulation can be fused, as this does not involve loss of featural information.

There are two ways to retain Baković's (Reference Baković2017) insight in an ACC analysis, and thus treat the reduction as driven by *ComplexCoda ranked above Max(•). One is to assume that Catalan cluster simplification involves vacuous spreading and that the surface segment dominates two identical place nodes (e.g. [coronal] in [pɔn]). This makes it possible to block deletion of segments in heterorganic clusters by ranking two constraints above *ComplexCoda: Max[place], which ensures that deletion can only apply if the place features dominated by the deleted root node can be associated with another, properly integrated, host, and *Contour, which militates against root nodes dominating non-identical place features. Another way to view the data is to assume that segment deletion is preceded by non-reductive coalescence (discussed in §3.5), resulting in homorganic sequences sharing a single set of place features. In this case, cluster reduction of heterorganic codas can be blocked by a Max[place] constraint. The constraint is satisfied when a segment in a homorganic sequence is deleted, because the place feature it dominates is still properly integrated, thanks to its association to the retained host.

Another kind of data that has been argued to involve crucial vacuous coalescence pertains to morphological haplology, where an affix or a part thereof apparently fails to surface in the context of a featurally identical or near-identical string. De Lacy (Reference de Lacy, de Lacy and Nowak2000) argues for an analysis in which haplology is driven by a general markedness constraint, such as *Struc, rather than any specific identity-avoidance constraint. *Struc is satisfied by fusion of identical segments, as this is the only way to reduce structure without loss of featural information. De Lacy provides evidence against treating at least some cases of morphological haplology, in Japanese and in French, as the result of deletion of the repeated material, either from the stem or from the affix. In Japanese, the evidence is related to the way haplology interacts with accentuation, while in French it is related to the restrictions on the shape of morphemes that can haplologise.

An attempt at an ACC analysis of morphological haplology that treats it as vacuous spreading of individual features or subsegmental nodes (as suggested above for the place node in Catalan) is unlikely to be successful, as it would involve massive violations of constraints on locality, making it impossible to restrict haplology to adjacent strings. However, the framework offers a different way to derive the patterns described by de Lacy, by extending the ACC analysis of subtractive morphology developed by Zimmermann (Reference Zimmermann2013, Reference Zimmermann2017) and Trommer & Zimmermann (Reference Trommer and Zimmermann2014) to morphological haplology. In their proposal, subtractive morphology (shortening or deletion of a segment or segments) is attributed to the affixation of a prosodically defective morpheme, which either lacks some prosodic structure (a mora or a syllable) or consists of floating prosodic nodes that are not associated to any melody. An analysis of haplology in these terms could treat it as the affixation of drifting melodic material to stems prosodified at a previous stratum, resulting in the affix ‘usurping’ some of the stem's prosodic nodes, leading to delinking of the melody that they underlyingly dominate. In contrast to general subtractive morphology, usurpation would have to be controlled by *Contour constraints which would only allow association to prosodic nodes affiliated with the stem if the segments dominated by those nodes are identical.

While a full analysis of haplology as subtractive morphology would take us too far afield, I briefly outline how this approach could be used to analyse Japanese and French haplology in terms of the underparsing of stem material. In Japanese, haplology affects the Classical Japanese predicative suffix [-ɕi], which repels a stem-final accent in underlyingly accented stems, shifting it to the stem-penultimate syllable, e.g. [ɕíɾo-ɕi] ‘white (classical.pred)’ vs. [ɕiɾó-i] ‘white (modern.pred)’ (Lawrence Reference Lawrence and Haraguchi1997: 382). When the suffix is attached to accented stems ending in [ɕi], the haplologised form carries the accent on the penultimate syllable, e.g. [ɯɾé«ɕi»] ‘happy (classical.pred)’; cf. [ɯɾeɕí-i] ‘happy (modern.pred)’ (Lawrence Reference Lawrence and Haraguchi1997: 382). According to de Lacy, this argues against deletion of stem material, as it would predict accent shift to the stem-initial vowel (*[ɯ́ɾe∅-ɕi]). A containment-based account, however, makes it possible to view the haplologised form as one in which the stem syllable is not realised phonetically, but is nevertheless counted by the accent shift if the constraint that drives it is a general clone sensitive to the entire output structure.

In French, haplology affecting words formed with the nominal derivational suffix /-ist/, e.g. /bodis/ ‘Baudis (name)’ + /ist/ → [bod«is»t], /maʁini/ ‘Marini (name)’ + /ist/ → [maʁin«i»st] (Corbin & Plénat Reference Corbin and Plénat1992, de Lacy Reference de Lacy, de Lacy and Nowak2000), fails to apply when the stem ends in [ist], that is, when it is fully identical to the suffix, e.g. /ametist/ ‘amethyst’ + /ist/ → [ametistist], *[amet«ist»]. According to de Lacy, this speaks against viewing the process as deletion of the stem material, as it makes is impossible to block deletion when it would result in the non-realisation of a morpheme. In a usurpation account, where the suffix is represented as a melody without any prosodic structure, attached to prosodified stems, the restriction can be reinterpreted as a ban, enforced by a general clone constraint on syllable codas, on associating a fricative to a (covert) coda containing an obstruent cluster with falling sonority.

3.5 Non-reductive coalescence

Non-reductive coalescence affects two or more identical lower nodes in a feature-geometric tree, yielding a single node that is associated to multiple immediately dominating nodes. I propose that this type of coalescence should be decomposed into two operations: (i) delinking of all but one of the lower nodes in a sequence of adjacent identical nodes, leaving them uninterpreted phonetically, and (ii) spreading the remaining, phonetically realised, node onto the hosts that have lost their daughters, as in (10b).

I illustrate my account with a reanalysis of high-tone coalescence in Zezuru Shona, which, as noted in §2.2, has two level tones, high (ˊ) and low ( ). When a sequence of high tones is created across a stem boundary, one of two word-level lowering processes applies. If a high-toned stem is preceded by a sequence of more than one consecutive high-toned syllable, the last one of these is lowered by a process that Myers (Reference Myers1987, Reference Myers1997) calls Tone Slip, illustrated in (27a). If the stem is preceded by a single high-toned syllable, Meeussen's Rule lowers the tone of the stem, as in (b) (cf. (8) above).

1. (27)

   

Meeussen's Rule treats a sequence of adjacent high-toned syllables within a stem as a single unit, which results in lowering of the entire span. Myers accounts for this by arguing that the high tones had fused at the previous stratum. At the point at which Meeussen's Rule applies, the sequence of syllables is associated to a single high-toned node. A constraint protecting the left edge of a tonal span, Anchor(H)-L, ranked higher than Max(H), eliminates candidates in which only the leftmost stem syllable is lowered, favouring instead forms in which all syllables linked to the same tone have been affected.

Myers (Reference Myers1997) attributes coalescence at the stem level and tonal alternations at the word level to the Obligatory Contour Principle (OCP; Leben Reference Leben1973, Reference Leben and Fromkin1978, McCarthy Reference McCarthy1986). He assumes a version of the OCP constraint mediated by the syllable (the tone-bearing unit), whose ACC definition is given in (28).

1. (28)

   

A syllable-based definition of the OCP constraint is crucial, because Myers (Reference Myers1997: 853–854) assumes, on the basis of the phonological and phonetic inertness of the low tone, that the two surface tones are represented in terms of a privative opposition between the presence (high tone) and absence of tone (low tone). Forms containing two high-toned syllables separated by a phonetically low-toned, and hence phonologically toneless, syllable (where identical tones are adjacent at the tonal tier, but are not associated to adjacent TBUs) are shown to be grammatical, even though they would violate the generalised version of the constraint.

Myers (Reference Myers1997: 870–871) explains the difference in OCP-repair strategies at the stem and word levels by adopting a stratal organisation of the phonological component, in which progressively larger morphological domains are evaluated by grammars with potentially different rankings, with the output of one level of evaluation serving as input to the following level. In his analysis, the constraint ranking responsible for coalescence is restricted to the stem stratum. At the word stratum, the ranking is reversed in such a way that coalescence is no longer the optimal repair strategy for OCP(H) violations, which is why Meeussen's Rule applies instead. I adopt this approach, and additionally assume a ‘clean-up’ operation introduced by Trommer (Reference Trommer2011: 76), which applies between strata, removing any improperly integrated nodes and association lines, and assigning one common morphological colour to all remaining elements.

In the ACC reanalysis of the Shona tonal patterns, the OCP(H) constraint, ranked above Max(H), is responsible for the non-realisation of some input high tones, both as an independent repair at the word level and as a subcomponent of non-reductive coalescence at the stem level. The stem-level spreading subcomponent of coalescence is driven by Specify(σ,T), a phonetic clone of a constraint mandating that syllables be associated to tonal nodes, formulated in (29a).

1. (29)

   

To ensure satisfaction by high-tone spreading rather than high-tone epenthesis, Dep(T) has to be ranked higher than *Long(T) in (29b), a markedness constraint against multiply-linked tones. On its own, this ranking predicts that high tones should spread onto all toneless syllables, whether they are underlyingly underspecified or are linked to underlying high tones via association lines that have been made invisible in order to satisfy OCP(H), in violation of Specify(σ,T).Footnote ¹³ This is not the case. As shown in (30a), high tones in Shona do not spread leftwards onto toneless syllables at all. Rightwards, no spreading applies in nouns and adjectives either, as in (b).Footnote ¹⁴

1. (30)

   

To restrict spreading to those syllables that dominate delinked tones, Specify(σ,T) has to be outranked by a constraint that can block spreading onto underlyingly toneless syllables. This can be achieved with *σ´ in (31a), the general clone of a constraint penalising high-toned TBUs.

1. (31)

   

On this analysis, the spreading subcomponent of non-reductive coalescence displays a type of phonologically derived environment effect (Kiparsky Reference Kiparsky and Fujimura1973, Reference Kiparsky, Hargus and Kaisse1993), whereby a process only applies to structures derived by the application of another process.

The tableau in (32) illustrates the interaction of the relevant constraints with a stem-level evaluation of [sékúru] ‘grandfather’.

1. (32)

   

In the faithful candidate, (a), the initial and the second syllable each dominate a separate high tone. This configuration incurs a fatal violation of OCP(H). In candidates (b)–(d), this violation is avoided by delinking one of the offending tones, at the cost of violating Max(H). In (32b), delinking results in the candidate having two TBUs that are not overtly specified for tone. This does not help remove violations of *σ´, since it is a general clone which assesses the entire output structure, where the second TBU is still associated to a high tone. On the other hand, the next constraint in the hierarchy, Specify(σ,T), is a phonetic clone, which only assesses properly integrated material. Consequently, even though the second TBU dominates a covert high tone, this information is not accessible to Specify(σ,T), leading to a second violation and the elimination of the candidate. In (c), the retained tone spreads onto the syllable that has lost its underlying tone. The additional violation of Specify(σ,T) is therefore avoided. Spreading the first high tone onto the underlyingly high-toned following syllable violates *Long(T) and *Contour(T) in (31b), a general clone of a constraint penalising syllables associated to more than one tone, but these constraints are low-ranked, and do not affect the result. The evaluation also includes a candidate, (d), in which the retained high tone spreads even further, onto the underlyingly unspecified final syllable. This removes the last violation of Specify(σ,T), but incurs an additional violation of the higher-ranked *σ´, which results in the elimination of the candidate.

To recapitulate, non-reductive coalescence in Shona can be decomposed into the delinking of all but one of the adjacent high tones associated to neighbouring syllables, driven by a syllable-mediated OCP(H) constraint, accompanied by spreading of the retained tone onto the syllables whose association to underlying tones has been lost. Spreading is driven by Specify(σ,T), and kept in check by a general markedness constraint against high-toned syllables, *σ´, which prevents spreading onto underlyingly underspecified syllables.

At the word level, coalescence is no longer the optimal repair for OCP(H). This can be achieved by ranking *Contour(T), the constraint that militates against spreading onto an underlyingly specified syllable by penalising syllable nodes dominating multiple tonal nodes (covert or overt), above Specify(σ,T). Under this ranking, delinking a high tone becomes the optimal strategy to satisfy OCP(H). If delinking a tone from a single syllable results in the modification of the left edge of a tonal span (understood as a single tone associated to multiple TBUs), the associations linking it to all dominating TBUs are delinked instead, which has the effect of lowering an entire tonal span.