# Rounding contrast activation in Ngbugù: licensing and sub-segmental interactions

Charles Vancaeyzeele, Galla Althabégoïty

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Charles Vancaeyzeele, Galla Althabégoïty. Rounding contrast activation in Ngbugù: licensing and sub-segmental interactions. Radical: A journal of Phonology, 2025, 7, pp.32-86. hal-04962481v2

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radical

A Journal
of Phonology

ISSN 2592-656X

volume 7, 2025

Althabégoïty, Galla
Vancaeyzeele, Charles

Rounding contrast
activation in
Ngbúgù: licensing and
sub-segmental interactions

Althabégoïty, Galla & Charles Vancaeyzeele. 2025. "Rounding contrast activation in Ngbúgù: licensing and sub-segmental interactions". *Radical: A Journal of Phonology*, 7, 32-86.

Editor: Noam Faust

Reviewers: Shanti Ulfsbjorninn, Connor Youngberg and Fabian Zuk

CC-BY

https://creativecommons.org/licenses/by/3.0/

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PAPER
ROUNDING CONTRAST ACTIVATION IN
NGBÚGÙ: LICENSING AND SUB-SEGMENTAL
INTERACTIONS

ALTHABÉGOÏTY, GALLA (UNIVERSITY OF ORLÉANS, CNRS/LLL)

VANCAEYZEELE, CHARLES (UNIVERSITY OF ORLÉANS, CNRS/LLL)

The Ngbúgù language (Banda group, Ubangi family; Central African Republic) exhibits a contextual contrast between rounded and unrounded vowels; the two contrasts /o/ vs /ɔ/ and /u/ vs /ʊ/ only apply in seven contexts: k_, g_, kʷ, gʷ, ɔ_, ɔʷ and ugʷ. Given the scarce distribution of this contrast, we suggest it is activated in these contexts, rather than neutralized elsewhere. Relying on the frameworks of Element Theory (Kaye et al. 1985, 1990, Backley 2011), Government Phonology (Kaye 1990, Kaye et al. 1990, Charette 1990, 1991), and Feature Geometry (Clements 1985, Sagey 1986, Clements and Hume 1995) suited for elements (Harris and Lindsey 1995, Ulfsbjorninn 2021), we provide a representational analysis in which the |U| element is responsible for this activation.

**Keywords:** Ngbúgù (Banda, Ubangi), rounding contrast, Government Phonology, Element Theory, Feature Geometry
INTRODUCTION

The Ngbúgù language is spoken in the Central African Republic (90,000 speakers, according to Ethnolog's latest record), in the Basse-Kotto region. It is classified in South Central Banda, one of the several dialect clusters making up the Banda language group. The Banda group itself belongs to the hypothetical Ubangi language family, assumed to be part of the Niger-Congo phylum (Cloarec-Heiss 1988, ISO: lnl in glottolog). To this day, the phonological system of Ngbúgù has been the topic of five publications (Théret-Kieschke 1998, Boyeldieu and Cloarec-Heiss 2001, Touguele 2008, Althabégoïty 2019, Olson 2022) and one PhD thesis (Althabégoïty 2024). The present study is based on firsthand data which were collected from two speakers from the city of Alindao, who were living in France at the time of data collection. The data are consistent with Boyeldieu's (1989, available on RefLex, Segerer and Flavier 2011) but not with Olson's (2022).

The data show a rounding contrast between [o] and [] on one hand, between [u] and [u] on the other. Both contrasts appear to be restricted to a few contexts, which all share a velar component: g_, gв_, k_, кв_ к_, ʃgк_ and ʔк_. For instance, whereas the verbal forms [gw] ‘to leave, to insult’ and [gu] ‘to grow up, to be far away’ are in opposition, [tʃu] and [tʃu] ‘to die’ happen to be in free variation. This contrast is entirely phonologically conditioned; morphology does not interfere in it whatsoever. Our key proposal is the following: the rounding contrast is activated in contexts it appears in, rather than neutralized in contexts which lack it. This interpretation is warranted by the empirical fact that the latter set of contexts greatly outnumber the former.

The contrast activation is accounted for using the tools of Government Phonology (Kaye 1990, Kaye et al. 1990, Charette 1990, 1991), Element Theory (Kaye et al. 1985, 1990, Backley 2011) and Feature Geometry (Clements 1985, Sagey 1986, Clements and Hume 1995) suited for phonological elements (Harris and Lindsey 1995, Ulfsbjorninn 2021). Crucially, both velar consonants and back vowels contain a |U| element, which
may also be used to encode rounding within the latter type of segments (cf. Backley and Nasukawa 2009). The overall idea that is defended here is the following: The nucleus may extract a |U| element out of the onset in order to acquire contrastive rounding.

To achieve this, we stipulate a three-step phonological analysis. First, the nucleus (hosting underspecified /O/ or /U/) licenses the preceding onset. Second, the element matrix of the place of the nucleus is copied through the application of a ‘SEARCH&COPY’ mechanism (cf. Nasukawa 2016). Third, the copied material is sent to the place node of the nucleus as a floating melody. This final step involves the activation (or lack thereof) of contrastive rounding, which depends on the nature of the copied material. If only a |U| element is copied, it has two possibilities: either it associates to the element structure (deriving rounded /o/ or /u/), or it does not (deriving unrounded /ʊ/ or /u/). If any other kind of melodic material is copied, however, the potential merge operation incurs a derivational crash; in this case, /O/ or /U/ remain underspecified, and no rounding contrast is obtainable inside the nucleus.

The paper is structured as follows. Section 1 presents the methodology of data collection and introduces the rounding contrast in more detail. Section 2 describes the tools which will help identify the relation between segments at relevant levels of the phonological structure. The account of the Ngbúgù facts is given in section 3.

# 1. THE ROUNDING CONTRAST BETWEEN BACK VOWELS

## 1.1. THE CONSONANTS AND VOWELS OF NGBÚGÙ

The rounding contrast has been identified in first-hand data collected by Althabegoïty (2019), with the assistance of Anicet Ossibouyen Senganambi, a native speaker originating from the city of Alindao (Basse-Kotto, Central African Republic), who resided in France at that time. The data collection was conducted in two stages. First, a set of basic lexical items from the Greenberg list, to which was added some Tervuren supplement
(translated and adapted into Gabonese languages by J. Blanchon), were elicited in isolation. Second, once segments were identified, the data were enriched with the manipulation of phonological paradigms, i.e. all possible combinations of consonants and vowels were elicited.

The same data set was used to establish the inventory of Ngbúgù phonemic segments; consonants are shown in table (1) and vowels in table (2). Consonantal phonemes between parentheses are considered marginal ([r] is only attested in loanwords, and [h] in ideophonic expressions). This inventory aligns with those identified by Boyeldieu and Cloarc-Heiss (2001:190) and Touguele (2008:69). It slightly differs from Théret-Kiescke's (1998:32), however, who proposes a distinct segmental analysis that involves affricate sounds.

(1) CONSONANT PHONEMES OF NGBÚGÙ

<table><thead><tr><th></th><th>LABIAL</th><th>ALVEOLAR</th><th>PALATAL</th><th>VELAR</th><th>LAB.-VEL.</th><th>GLOTTAL</th></tr></thead><tbody><tr><th>PLOSIVE</th><td>p b</td><td>t d</td><td>ʃ ʃʒ</td><td>k g</td><td>kp ʃb</td><td>ʔ</td></tr><tr><th>FRICATIVE</th><td>f v</td><td>s z</td><td>ʃ ʒ</td><td></td><td></td><td>(h)</td></tr><tr><th>NASAL</th><td>m</td><td>n</td><td>ɲ</td><td>ɲ</td><td>ɲ</td><td></td></tr><tr><th>LIQUIDS</th><td></td><td>l (r)</td><td>j</td><td>ɲ</td><td>w</td><td></td></tr><tr><th>PRE-NASALIZED</th><td>m b</td><td>n d</td><td>n ʃʒ</td><td>ɲ</td><td>ɲ</td><td>ɲ</td></tr><tr><th>IMPLOSIVE</th><td>b</td><td>d</td><td></td><td></td><td></td><td></td></tr></tbody></table>

<footnote n="1">¹ Boyeldieu and Cloarc-Heiss (2001) report that surface nasal velars are systematically followed by [w]. Accordingly, they admit the possibility that [ŋw] sequences might, underlyingly, form a single objet (i.e. a labialized nasal velar). This is the only case where [w] segments are treated as such. For more information about the overall behaviour of [w], please see fn. 7.</footnote>

<footnote n="2">² The /b/ segment is phonetically uvular, yet we choose to interpret it as a phonological velar. This treatment is justified on structuralist accounts (cf. Trubetzkoy 1939). If we were to add an extra ‘uvular’ column to include it in table (1), we would considerably constrain the proportional oppositions between /b/ and other objects, since no other segment is phonetically uvular. A virtual bilateral opposition between, let’s say, nasals and liquids, would in this case be: $\frac{n}{1} = \frac{n}{j} = \frac{ŋ}{\emptyset} = \frac{\emptyset}{k}$. This relation, logically defective since the last two fractions are lacking either a nominator or denominator value, indicates that uvular /b/ is not, in this case, in opposition with a nasal segment (as well as /ŋ/ with liquids, for that matter). One solution to this problem</footnote>
As for vowels, there is a distinction between three degrees of aperture (high, mid and low) and frontness (back, central and front). Additionally, a rounding contrast monopolarized by back vowels (boldfaced) is also attested.<fnref n="3" /> <fnref n="4" />

(2) VOWEL PHONEMES OF NGBÚGÙ

<table><thead><tr><th></th><th>FRONT</th><th>CENTRAL</th><th>BACK</th></tr></thead><tbody><tr><th>HIGH</th><td>i</td><td>i̥</td><td>w̥ u</td></tr><tr><th>MID</th><td>e</td><td>ə</td><td>ɣ̥ o</td></tr><tr><th>LOW</th><td></td><td>a</td><td></td></tr></tbody></table>

Again, this inventory digresses from previous works in some regards. For example, Theret-Kieschke (1998), Touguele (2008) and Olson (2022) do not acknowledge the [o] vs [ɣ] rounding contrast, which is instead interpreted as a lowness contrast ([o] vs [ɔ]).<fnref n="5" /> Also, [ɣ] in our data corresponds to [ɔ] in the works of these three authors. The realization of this segment is less rounded and lower than [o]. Our decision to represent it as [ɣ] relies on its own distribution, as well as the organization of the vocalic system. Because [u] and

is to render the relation operational by fusing the ‘velar’ and the ‘uvular’ categories, giving: $\frac{n}{l} = \frac{n}{j} = \frac{n}{k}$. This phonologically more stable series of opposition suggests that [k] is best considered, underlyingly, a velar. Note that this treatment is reminiscent of Boyeldieu and Cloarec-Heiss’ (2001), for whom uvular and velar realizations altogether form the category of ‘posterior’ consonants.

Also, two reviewers suggest that we employ the IPA symbol /ɣ/ (voiced velar fricative) to represent this segment. This would indeed better fit its phonological identity. We choose, nonetheless, to maintain the ‘uvular’ representation, for the sake of consistency with the literature (cf. Boyeldieu and Cloarec-Heiss 2001).

<footnote n="3">³ Ngbúgù also has a tonal system, in which three values are attested: low (v̵), medium (v̄) and high (v́).</footnote>

<footnote n="4">⁴ Boyeldieu and Cloarec-Heiss (2001) and Olson (2022) have also identified a few diptongs, which are not relevant in the present study.</footnote>

<footnote n="5">⁵ Olson identifies three different mid back vowels (/ɔ/, /o/ and /ɔ/), whereas we acknowledge only two: /o/ and /χ/. This discrepancy rests on two key points. First, every /ɔ/ segment in Olson’s data aligns with /χ/ in ours. Second, the minimal pairs which legitimate the /o/ vs /ɔ/ opposition in Olson are interpreted differently in our corpus. Here are a few examples: i) [kpɔtɔ] ‘hat’ contrasts with [kpɔtɔ] ‘skin’ in his, but [kpɔtɔ] is a homophonous form for ‘hat’ and ‘skin’ in ours; ii) the opposition between [kɔ] ‘male’ and [kɔ̥] ‘type of termite’ in Olson’s description corresponds to a tonal alternation for us ([kx̥] ‘male’ and [kx̥] ‘type of termite’); iii) [dɔ] ‘divert’ and [tɔ] ‘marry’ are alternatively transcribed [dχ] ‘turn’ and [tχ] ‘marry’, etc.</footnote>
[w] are in opposition in the same contexts as [ɣ] and [o], we consider that they equally contrast in rounding. An interesting fact to point out is the very limited distribution that afflicts the rounding contrast between back vowels ([u] vs [w] and [o] vs [ɣ]).<fnref n="6" /> The relevant data is introduced in the next section.

**1.2. THE DISTRIBUTION OF THE ROUNDING CONTRAST**

The analysis we provide of the rounding contrast solely relies on minimal pairs. Before introducing the data, we focus on the methodology adopted to build the corpus presented in this section.

As an isolating language, Ngbúgù stores numerous monosyllabic morphemes in its lexicon. This peculiarity greatly reduces the probability of finding morphophonologically conditioned allomorphy, as combinatorial possibilities between morphemes are very restrained. In fact, any kind of allomorphic variation is very likely to be free. As a result, an adequate identification of minimal pairs could not be achieved through a simple observation of transcribed wordlists. Chances are, in cases where transcriptions are done before acquiring a sufficient comprehension of the language phonology, one might misinterpret the relation between a surface form and its underlying representation. Consider, for example, the two homophonous morphemes /ŋgú/ ‘water’ and /ŋgú/ ‘year’, both potentially realized [ŋgú] and [ŋgwú].<fnref n="7" /> If only the realization [ŋgwú] were captured for ‘year’ and the other realization [ŋgú] for ‘water’, one would most certainly (and incorrectly) hypothesize the existence of a contrast between [ú] and [wú].

<footnote n="6">⁶ One reviewer asks if these inconsistencies, raising from one transcription to another, could be attributed to dialectal variation. Unfortunately, the data we have access to are too limited to answer to this question.</footnote>

<footnote n="7">⁷ In velar environments, [w] tends to freely alternate with Ø. Other examples are [βØo]~[ðwo] ‘to take a walk’, [kØo]~[kwo] ‘to take’, yet only before rounded vowels (cf. [ðγ]/[kγ], but *[ðwx]/*[kwx]). It is important to mention that this alternation is not contrastive. The only exception to this particular behavior of [w] applies to nasal velars, which are systematically followed by it (cf. fn. 1; examples can also be found in table 6 below). For reasons of space, this phenomenon is left aside in this paper. We refer the reader to Boyeldieu and Cloarec-Heiss (2001), who provide a thorough discussion on this topic.</footnote>
To reduce the risk of misinterpreting the data, we checked the differences in meaning induced by the commutation of one vowel within complete sentences produced by our two Ngbúgù informants. Examples are given in (3). On one hand, (3a) and (3b) unambiguously reveal a first contrast between the mid back segments [o] and []. On the other hand, the comparison between (3c) and (3d) indicates a second contrast between their high counterparts [u] and [u] (alternating back vowels are underlined).

<table><tr><td>(3) a.</td><td>[fè kā là ká-kò má'gỳ]</td></tr><tr><td></td><td>3AN.SBJ be with INF-take mango</td></tr><tr><td></td><td>'She/he is taking mango.' [ASEL25_148]</td></tr><tr><td>b.</td><td>[fè kā là ká-kỳ má'gỳ]</td></tr><tr><td></td><td>3AN.SBJ be with INF-pick mango</td></tr><tr><td></td><td>'She/he is picking mango.' [ASEL25_149]</td></tr><tr><td>c.</td><td>[mē gú ná]</td></tr><tr><td></td><td>1SG.SBJ grow_up already</td></tr><tr><td></td><td>'I grew up already.' [AREL13_123]</td></tr><tr><td>d.</td><td>[mē gú ná]</td></tr><tr><td></td><td>1SG.SBJ leave already</td></tr><tr><td></td><td>'I left already.' [AREL13_118]</td></tr></table>

This issue now settled, it is important to note that the rounding contrast in back vowels is not systematic. Table (4) shows occurrences of monosyllabic CV morphemes in which the contrast either takes place or not.<fnref n="8" /> Each row is associated with one place of articulation for the preceding consonant. The two columns distinguish between rounded (left) and unrounded (right) realizations of one back vowel.

<footnote n="8">⁸ We thought it best to remove tones from now on, since they are irrelevant to the current discussion. In each pair of each upcoming table, though, both items contain the same tone as to guarantee the exclusive implication of the alternation in rounding between two semantically different items.</footnote>
(4) DISTRIBUTION OF THE ROUNDING CONTRAST IN CV SYLLABLES

<table><thead><tr><th></th><th>ROUNDED</th><th></th><th>UNROUNDED</th></tr></thead><tbody><tr><td rowspan="2">a.</td><td>[ko] ‘to take’</td><td>vs</td><td>[kɔ] ‘to pick’</td></tr><tr><td>[ku] ‘to jump’</td><td>vs</td><td>[kw] ‘to drip’</td></tr><tr><td rowspan="2">b.</td><td>[ʔo] ‘to shout’</td><td>~</td><td>[ʔɔ]</td></tr><tr><td>[ʔu] ‘to break’</td><td></td><td>N/A</td></tr><tr><td rowspan="2">c.</td><td>[po] ‘to talk’</td><td>~</td><td>[pɔ]</td></tr><tr><td>[pu] ‘to look for’</td><td>~</td><td>[pwo]</td></tr><tr><td rowspan="2">d.</td><td>[tʃo] ‘to taste good’</td><td>~</td><td>[tʃɔ]</td></tr><tr><td>[tʃu] ‘to die’</td><td>~</td><td>[tʃu]</td></tr><tr><td rowspan="2">e.</td><td>[to] ‘to originate’</td><td>~</td><td>[tɔ]</td></tr><tr><td>[tu] ‘ear’</td><td>~</td><td>[tw]</td></tr><tr><td>f.</td><td>[kpo] ‘to grow up’</td><td></td><td>N/A</td></tr></tbody></table>

Interestingly, minimal pairs are identifiable in velar contexts (4a), but not in laryngeal (4b), labial (4c), palatal (4d), alveolar (4e) and labio-velar (4f) contexts. All of the onsets in table (4) share the same value for voicing (i.e. voiceless) and manner of articulation (i.e. plosive). It turns out, then, that only place of articulation can be a conditioning factor for the rounding contrast to occur.

Places of articulation which block the contrast are consistent in their behavior, no matter the specification for voicing and manner of the onset. This is shown in table (5), in which labial (5a), palatal (5b) and alveolar (5c) contexts are enriched with voiced and non-plosive segments.<fnref n="9" /> In any case, no minimal pair is attested.

<footnote n="9">⁹ Table (5) does not include laryngeals nor labio-velars. The former can only be plosive and voiceless in Ngbúgù (excluding [h] which, once again, is marginalized due to its exclusive appearance in ideophonic expressions), while the latter is only instantiated by [kp] in our data (at least in these contexts).</footnote>
(5) NO INTERFERENCE OF VOICING AND MANNER

<table><thead><tr><th></th><th>ROUNDED</th><th>UNROUNDED</th></tr></thead><tbody><tr><td rowspan="10">a.</td><td>[po] ‘to talk’</td><td>~ [px]</td></tr><tr><td>[bo] ‘termite’</td><td>~ [bx]</td></tr><tr><td>[vo] ‘to pinch by scratching’</td><td>~ [vx]</td></tr><tr><td>[fo] ‘to rot’</td><td>~ [fx]</td></tr><tr><td>[mo] ‘to laugh’</td><td>~ [mx]</td></tr><tr><td>[pu] ‘to look for’</td><td>~ [pw]</td></tr><tr><td>[bu] ‘to blacken’</td><td>~ [bw]</td></tr><tr><td>[fu] ‘to be good’</td><td>~ [fw]</td></tr><tr><td>[fso] ‘to taste good’</td><td>~ [fs]</td></tr><tr><td>[dzo] ‘to crouch’</td><td>~ [dz]</td></tr><tr><td rowspan="5">b.</td><td>[fzu] ‘to die’</td><td>~ [fzw]</td></tr><tr><td>[dzu] ‘back’</td><td>~ [dzw]</td></tr><tr><td>[fzu] ‘to be bitter’</td><td>~ [fzw]</td></tr><tr><td>[zu] ‘to burn (intr.)’</td><td>~ [zw]</td></tr><tr><td>[nu] ‘to cook’</td><td>~ [nw]</td></tr><tr><td rowspan="4">c.</td><td>[to] ‘to originate’</td><td>~ [tx]</td></tr><tr><td>[do] ‘to turn’</td><td>~ [dx]</td></tr><tr><td>[tu] ‘ear’</td><td>~ [tw]</td></tr><tr><td>[du] ‘to age’</td><td>~ [dw]</td></tr></tbody></table>

The situation is different for velar onsets. More examples of this context are given in table (6). Even though voicing has no influence on the presence of the rounding contrast either (6a), manner cannot be so simply discarded. While plosives (6a) and the liquid /k/ (6b) do favor the contrast, no minimal pair is attested in segments exhibiting a nasal resonance, i.e. nasal (6c) and pre-nasalized (6d) consonants.
(6) INTERFERENCE OF MANNER ONLY IN VELAR CONTEXTS

<table><thead><tr><th></th><th>ROUNDED</th><th></th><th>UNROUNDED</th></tr></thead><tbody><tr><td rowspan="4">a.</td><td>[ko] ‘to give’</td><td>vs</td><td>[kɔ] ‘to pick’</td></tr><tr><td>[go] ‘hunger’</td><td>vs</td><td>[gɔ] ‘territory’</td></tr><tr><td>[ku] ‘to jump’</td><td>vs</td><td>[ku] ‘to drip’</td></tr><tr><td>[gu] ‘to grow up’</td><td>vs</td><td>[gw] ‘to leave’</td></tr><tr><td>b.</td><td>[ɔo] ‘to take a walk’</td><td>vs</td><td>[ɔχ] ‘to dry’</td></tr><tr><td rowspan="2">c.</td><td>[ŋ̥wo] ‘to kill’</td><td></td><td>N/A</td></tr><tr><td>[ŋ̥wu] ‘to see’</td><td></td><td>N/A</td></tr><tr><td rowspan="2">d.</td><td>N/A</td><td></td><td>[ŋ̥gx] ‘breast’</td></tr><tr><td>[ŋ̥gu] ‘water’</td><td></td><td>N/A</td></tr></tbody></table>

At this point, we can already establish that the rounding contrast cannot be allowed unless two conditions are met: i) the onset is velar; ii) the onset has no nasal component.

Complex onsets add more complexity to the situation. Table (7) contains examples whose onsets are composed of a second member [ɔ]. Unsurprisingly, complex velars (7a) do allow the rounding contrast, though complex labials (7d), alveolars (7e), palatals (7f) and labio-velars (7g) do not. These latter contexts remain consistent with that of their simplex configuration. However, complex laryngeals (7b) and pre-nasalized velars<fnref n="10" /> (7c) unexpectedly allow the rounding contrast.

<footnote n="10">¹⁰ Although complex pre-nasalized velars do exist in Ngbúgù, the same cannot be said for complex nasal velars (cf. *[ŋ̥ɔ]).</footnote>
(7) DISTRIBUTION OF THE ROUNDING CONTRAST IN C<sub>8</sub>V SYLLABLES

<table><thead><tr><th></th><th>ROUNDED</th><th></th><th>UNROUNDED</th></tr></thead><tbody><tr><td rowspan="2">a.</td><td>[кво] ‘to stop’</td><td>vs</td><td>[квх] ‘to open’</td></tr><tr><td>[гво] ‘to touch’</td><td>vs</td><td>[гвх] ‘to sweep’</td></tr><tr><td>b.</td><td>[?во] ‘to whistle’</td><td>vs</td><td>[?вх] ‘to scold’</td></tr><tr><td>c.</td><td>[?гво] ‘to scratch’</td><td>vs</td><td>[?гвх] ‘to make a detour’</td></tr><tr><td rowspan="4">d.</td><td>N/A</td><td></td><td>[рвх] ‘egg’</td></tr><tr><td>N/A</td><td></td><td>[fvх] ‘to rub’</td></tr><tr><td>N/A</td><td></td><td>[vвх] ‘to pour’</td></tr><tr><td>N/A</td><td></td><td>[dвх] ‘red’</td></tr><tr><td rowspan="4">e.</td><td>N/A</td><td></td><td>[твх] ‘to wipe’</td></tr><tr><td>N/A</td><td></td><td>[sвх] ‘to tear’</td></tr><tr><td>N/A</td><td></td><td>[звх] ‘to be slippery’</td></tr><tr><td>N/A</td><td></td><td>[fвх] ‘to tighten’</td></tr><tr><td>f.</td><td></td><td></td><td></td></tr><tr><td>g.</td><td>[квро] ‘repeatedly’</td><td></td><td>N/A</td></tr></tbody></table>

In sum, only 7 consonantal contexts allow the rounding contrast between back vowels: ‘oral’ (i.e. non nasal) velars k_, g_, в_, кв_ and гв_, the pre-nasalized velar гвх_ and the laryngeal ?в_. Based on these facts, we hypothesize that the rounding contrast is not ‘neutralized’ in cases it is unattested, but ‘activated’ in cases it is attested. This interpretation is warranted by the Occcam’s razor principle. Stating the condition(s) for the manifestation of a statistically marginal<fnref n="11" /> phenomenon (in this case, contrastive rounding) requires less information than stating the condition(s) for its absence. Positing a contrast activation will thus unquestionably limit the complexity of the analysis of the Ngbúgù data. Our proposal is all the more justified that no rounding contrast is attested in onsetless contexts

<footnote n="11">¹¹ We mean ‘marginal’ in terms of the number of contexts, not the total number of lexical items recorded in the lexicon. We thank one of our reviewers for prompting us to clarify this distinction.</footnote>
(Ø_) either. It seems to us, then, that the contrast is by default inoperative, though rises in
case back vowels are inserted in one out of the seven contexts listed above.

We list the relevant questions regarding the rounding contrast activation in (8). Section
2 introduces the theoretical background that will help provide an answer to those ques-
tions.

(8) a. Why do ‘oral’ velars activate the rounding contrast?

b. Why do alveolars, palatals, labials and labio-velars block the contrast activation?

c. How can we explain the ambiguous behaviour of simplex vs complex laryngeals and ‘nasal’ velars?

## 2. LICENSING AND COPY

In section 1.2, we established that the nature of the onset conditions the rounding contrast activation between back vowels. Interpreting the Ngbúgù facts therefore requires to specify i) the relation between segments and ii) the material they contain. Our theoretical framework, which covers these two aspects, falls within Government Phonology (Kaye 1990, Kaye *et al.* 1990, Charette 1990, 1991), Element Theory (Kaye *et al.* 1985, 1990, Backley 2011) and Feature Geometry (Clements 1985, Sagey 1986, Clements and Hume 1995) suited for elements (Harris and Lindsey 1995, Ulfsbjorninn 2021). The first one is introduced in section 2.1, and the other two in section 2.2. Section 2.3 shows how these tools combine to generate the rounding contrast.

### 2.1. LICENSING AND GOVERNMENT-LICENSING

In Government Phonology (GP), syllabic constituents are bound by relations which con-
dition different aspects of their phonological identity: government and licensing. For in-
stance, onsets (O) are required to be licensed by their nucleus (N) to take part in the for-
mation of a syllable (Kaye 1990, Kaye *et al.* 1990, Charette 1990, 1991, Harris 1994).<fnref n="12" />

<footnote n="12">¹² In Kaye (1990) and Kaye *et al.* (1990), this lateral support is provided by government, later re-attributed to licensing by Charette (1990, 1991) and Harris (1994).</footnote>
This situation is shown in (9a). Similarly, the complement inside a branching<fnref n="13" /> onset (typically instantiated by ‘obstruent + liquid’ sequences) needs the lateral support provided by its head. In this configuration, illustrated in (9b), the head (x₁) governs its complement (x₂).<fnref n="14" /> Crucially, head-to-complement government is only possible if the head is licensed by a succeeding N; this is called government-licensing (Charette 1990, 1991).<fnref n="15" />

<figure><img src="image_4.png" /><figcaption>b. Government-licensing</figcaption></figure>

<figure><img src="image_5.png" /></figure>

Charette’s government-licensing mechanism was initially posited to explain the sustainability of complements relatively to their head and, by extension, to the succeeding nucleus. To be more accurate, a nucleus cannot be properly governed (and therefore be silent) if it follows a branching onset. The schwa in the French example [mɛgɛ̃mɑ̃] ‘poorly’ illustrates this situation. In a nutshell, Charette claims that /ə/ resists the influence of proper government (cf. *[mɛgɛ̃mɑ̃]) because it is necessary to sustain the preceding cluster; it licenses the head /g/, which in turn governs its complement /k/.

Besides binding syllables together, inter-constituent relations also influence the potential of segmental contrasts (Harris 1990, 1994, Cyran 2001, 2010). In Cyran’s theory of Complexity Scales and Licensing (CSL), the more segmentally complex a consonant is,

<footnote n="13">¹³ Auto-segments qualify as ‘branching’ if they associate to (at least) two other auto-segments positioned at a lower auto-segmental level.</footnote>

<footnote n="14">¹⁴ The object ‘x’ is called a ‘skeletal slot’ (or ‘x-slot’). In GP, x-slots represent the temporal dimension of a segment, which may not be realized unless it associates to one.</footnote>

<footnote n="15">¹⁵ In the earliest version of GP (represented by the authors referred to so far), governing/licensing relations were bi-directional. This bi-directionality was handed over to exclusively right-to-left relations in Strict CV (Lowenstamm 1996, Scheer 2004), at least for most of its practitioners. Rightward head-to-complement government (as part of Charette’s government-licensing hypothesis) has several equivalents in Strict CV: Scheer’s (2004) Infrasegmental Government (a leftward relation) and Ulfsbjorninn’s (2017) Indirect Government-Licensing (in which rightward head-to-complement government is maintained) are two examples.</footnote>
the more ‘licensing strength’ a following nucleus must exhibit. A few examples from Malayalam (borrowed from Cyran 2001:18) are given in table (10). The three rows show consonants with relative segmental complexity:<fnref n="16" /> sonorants (a) are made of two elements, while obstruents (b) have three and ‘laryngeally marked’ obstruents<fnref n="17" /> (c) potentially even more.

(10) COMPLEXITY SCALES AND LICENSING

<table><thead><tr><th></th><th>SEGMENT</th><th>ELEMENTS</th><th>LICENSER</th><th>EXAMPLES</th></tr></thead><tbody><tr><td>a.</td><td>[n]<br>[m]</td><td>(A, N)<br>(U, N)</td><td>Ø</td><td>[awanØ]<br>[mar'amØ]</td><td>'he'<br>'tree'</td></tr><tr><td>b.</td><td>[s]</td><td>(A, h, H)</td><td>[ə]</td><td>[ka'talaasə]</td><td>'paper'</td></tr><tr><td>c.</td><td>[bʰ]<br>[d]</td><td>≥ 3 elements</td><td>[a]</td><td>[laabʰam]<br>[madam]</td><td>'profit'<br>'intoxication'</td></tr></tbody></table>

Crucially, consonants which have more than three elements require licensing from a lexically filled nucleus, i.e. [a] in (10c) (e.g. [laabʰam] ‘profit’). A nucleus realized with epenthetic schwa, however, may only license consonants with at most three elements, as in (10b) (e.g. [ka'talaasə] ‘paper’). Empty nuclei are even less efficient in this regard: they cannot license consonants which contain more than two elements, as shown in (10a) (e.g. [mar'amØ] ‘tree’). The Malayalam data therefore strongly indicate that licensing determines the number of segments available at targeted consonantal positions.<fnref n="18" />

<footnote n="16">¹⁶ In CSL, segments are represented with elements. The list of elements (non-exhaustive) used by Cyran in table (10) includes: |A| (coronality), |U| (labiality), |N| (nasality), |h| (noise) and |H| (aspiration). These objects are introduced in section 2.2. Note, however, that the set of elements (and their values) used in this paper differs from Cyran’s.</footnote>

<footnote n="17">¹⁷ These are obstruents with extra laryngeal properties, such as voicing and aspiration. Cyran is not explicit about the composition in elements of such segments. He claims, however, that they ‘might be a bit more complex than all those followed by schwa’ (p. 18), as in row (b).</footnote>

<footnote n="18">¹⁸ For a more recent interpretation of this idea, see Cavirani & van Oostendorp (2019), where morphological status endows elements with more ‘phonological licensing power’.</footnote>
## 2.2. THE REPRESENTATION OF NGBÚGÙ SEGMENTS

### 2.2.1. ELEMENTS AS PHONOLOGICAL PRIMES

Element Theory (ET) manipulates objects called ‘elements’, which are taken to be the sole primitives of the phonological component. We use Backley’s (2011) repertoire, which counts six: three manner elements |H|, |L|, |?| (approximately corresponding to manner of articulation) and three place elements |A|, |U|, |I| (approximately corresponding to place of articulation for consonants and quality for vowels). In ET, the substance of each segment in a given language is represented by either one element or a combination of two or more elements.

Starting with vowels, unmarked systems which attest only the five peripheral segments (such as Spanish) will contain the following representations: [a] |A|, [i] |I|, [u] |U|, [e] |A I| and [o] |A U|.<sup>19</sup> In this case, |A| is associated with aperture, |I| with frontness and |U| with backness. Other tools may be required to fully grasp the contrastive potential of segments in more complex systems. One such tool is ‘headedness’, a formal hierarchical property of the relation between elements. This hierarchical relation establishes a distinction between ‘head’ elements and ‘non-head’ elements, the former being more prominent (phonetically and phonologically) than the latter (Harris and Lindsey 1995).<sup>20</sup> Headedness may encode a large array of different contrasts. For example, it has consistently been invoked since Smith (1988) to distinguish ATR segments from non-ATR ones (cf. Harris and Lindsey 1995, Charette and Göksel 1996, Cobb 1997). More recently, Backley (2011) proposed to use headedness as a way of contrasting high-mid with low-mid vowels, among other things.<sup>21</sup>

<footnote n="19"><sup>19</sup> In some non-standard versions of ET, the |A| element (as well as |H| and |?|) is converted into structure (cf. Pöchtrager 2006, 2018, Kaye & Pöchtrager 2013).</footnote>

<footnote n="20"><sup>20</sup> More generally, the fact that headedness leads to specific phonetic interpretations is supported in the following works: Harris (1994), Backley and Nasukawa (2009), Backley (2011), Breit (2013, 2017), Nasukawa (2016), among others.</footnote>

<footnote n="21"><sup>21</sup> See Zuk (2022) for a thorough presentation on headedness and its treatment in ET.</footnote>
As we saw in section 1, Ngbúgù has [w] and [ɣ] in its repertoire, which are the un-rounded versions of [u] and [o] respectively. As a consequence, it is necessary to add a distinction in rounding inside the representations of high back vowels and mid back vowels. Headedness, we believe, is perfectly warranted to achieve this. More precisely, we claim that non-head |U| is associated with unrounded back vowels [w] and [ɣ], and head |U| with their rounded counterparts [u] and [o]. In other words, while the |U| element represents backness, its status as a head represents rounding. This follows naturally from two considerations. First, rounding is a secondary property of the |U| element, alongside with backness (following Backley & Nasukawa 2009). Second, if head elements are indeed more prominent than their non-head equivalents, then they are expected to have a more phonetically accurate realization of the same basic phonetic cue that interprets the feature. This latter consideration is also in line with Breit's (2017) idea that some acoustic cues are incremental manifestations of the same element, depending on its status as a head or a non-head: Head |L|, for instance, expresses both voicing and nasality, while only voicing is encoded in its non-head |L| equivalent. Table (11) below shows the representations of the four back vowels of Ngbúgù (the other vowels are ignored).

<table><caption>(11) ELEMENTS FOR BACK VOWELS</caption><thead><tr><th></th><th>|U|</th><th>|L|</th></tr></thead><tbody><tr><td>Ø</td><td>w</td><td>u</td></tr><tr><td>|A|</td><td>ɣ</td><td>o</td></tr></tbody></table>

Crucially, we claim that the representations of the four back vowels in table (11) are only valid when they are contrastive in rounding. Recall, indeed, that this contrast is not systematic (see section 1.2). If so, the rounded and the unrounded segments in each of both pairs [u]~[w] and [o]~[ɣ] must share the same phonological representation. High and mid back vowels, unspecified for rounding, are thus associated with the underlying
segments /U/ and /O/, respectively. These will adopt the same configurations in elements than lexically unrounded /u/ and /ɔ/, i.e. |U| and |U.A|. Reasons behind this treatment will become clear in section 3.

As for consonants, most places of articulation are assigned a specific place element, either head or non-head. Again, the following representations are taken from Backley (2011): |U| (velarity), |U| (labiality), |I| (alveolarity) and |I| (palatality). In addition, labiovelars naturally display both |U| and |U|, whereas laryngeal segments have no place element. As demonstrated in section 1.2, manner of articulation has no influence on the rounding contrast of back vowels, except when it comes to velars: While plosives [k], [g] and liquid [k]<fnref n="22" /> allow the rounding contrast, nasal [ŋ] and pre-nasalized [ŋg] do not. For this reason, only the nasal element |L| is taken into consideration (the manner elements of frication |H| and occlusion |ʔ| are left aside). Table (12) shows the elements of Ngbúgù consonants which are relevant for our purpose.

(12) RELEVANT ELEMENTS FOR CONSONANTS

<table><thead><tr><th></th><th>|U|</th><th>|I|</th><th>|I|</th><th>|U|</th><th>|U.U|</th><th>Ø</th></tr></thead><tbody><tr><td>...</td><td>p b</td><td>t d</td><td>ʃ ʃʒ</td><td>k g</td><td>k̂p ĝb</td><td>ʔ</td></tr><tr><td>...</td><td>f v</td><td>s z</td><td>ʃ ʒ</td><td></td><td></td><td>(h)</td></tr><tr><td>|L|</td><td>m</td><td>n</td><td>ɲ</td><td>ŋ</td><td></td><td></td></tr><tr><td>...</td><td>l (r)</td><td></td><td>j</td><td>ɲ</td><td>w</td><td></td></tr><tr><td>|L|</td><td>m̂b</td><td>n̂d</td><td>n̂dʒ</td><td>ŋ</td><td>ŋg</td><td>ŋgb</td></tr><tr><td>...</td><td>b</td><td>d</td><td></td><td></td><td></td><td></td></tr></tbody></table>

<footnote n="22">²² Backley assigns a head |A| to uvular consonants. In our analysis, however, [k] is phonologically velar (cf. fn. 2).</footnote>
2.2.2. HEADEDNESS AS STRUCTURAL ASYMMETRY

The conception of headedness varies across the literature. The use of underscores to signal
head elements, as exemplified in section 2.2.1, is not uncontroversial. In this paper, we
follow Ulfsbjorninn's (2021) approach, where headedness is thought of as 'structural
asymmetry' within expressions.<fnref n="23" /> This inherent (i.e. non-templatic) approach to headed-
ness, called Bare Element Geometry (BEG), stems from the combined principles of ET,
Bare Phrase Structure (Chomsky 1993), Dependency Phonology (Anderson and Jones
1974, Anderson and Ewen 1987) and Feature Geometry (Clements 1985, Sagey 1986,
Clements and Hume 1995).

In opposition to x-bar inspired phonological structures which beg the question of
'where does the x-bar structure come from', complex element matrices in BEG are bi-
nary-branching arborescent structures built out of the merging of elements.<fnref n="24" /> The repre-
sentations in (13) offer an illustration of this architecture for each back vowel of Ngbúgù.
While the |U| element stands alone in the representation of the high unrounded segment
[u] (a), it merges with |A| to generate the mid unrounded segment [ɣ] (b). The represen-
tations of the rounded segments [u] (c) and [o] (d) require further clarification. In addition
to merging with another element, one element may also merge with another instance of
itself; Ulfsbjorninn calls this operation 'self-merge'. The representations in (c) and (d)
illustrate this phenomenon. In (d), after merging with |A|, |U| self-merges and conse-
quently merges with the projection (U, A), yielding the expression (U, (U, A)). In (c), |U|
self-merges twice: the first application of self-merge gives the structure (U, U), followed
by a second application which results in the expression (U, (U, U)).

<footnote n="23"><sup>23</sup> Also see the models of Precedence-free Phonology (Nasukawa 2011, 2012) and GP 2.0 (Pöchtrager 2006, 2018, Kaye & Pöchtrager 2013), where headedness is represented with structure as well.</footnote>

<footnote n="24"><sup>24</sup> The idea of using the merge mechanism to this end is first introduced in Breit (2013) (also see Breit 2017, 2023). As Ulfsbjorninn (2021) points out, Breit formally expresses headedness using the Kuratowski notation: ⟨a,b⟩ = {{a}, {a,b}} (which Chomsky’s 1995 definition of the merge operation: merge(α, β) = {α, {α, β}}), is based on). For instance, the compound expression |A.I| is rewritten as {{A}, {A, I}}, where |A| projects to a higher level by virtue of merging with |I|.</footnote>
(13)

a. /u/ |U|

U

c. /u/ (U, (U, U))

<figure><img src="image_6.png" /></figure>

b. /ʊ/ (U, A)

<figure><img src="image_7.png" /></figure>

d. /o/ (U, (U, A))

<figure><img src="image_8.png" /></figure>

The possibility for elements to self-merge allows to distinguish between ‘symmetrical’ expressions (cf. (a) and (b)) and ‘asymmetrical’ ones (cf. (c) and (d)). Symmetry is to be understood in BEG as a purely geometric property of representations: (c) and (d) are asymmetrical because their shape is different from that of their mirror image (on a vertical axis). In the lines of Dependency Phonology, asymmetry is taken by Ulfsbjorninn to be the true embodiment of headedness. Both structures in (c) and (d) are thus headed by virtue of the fact that (upper) |U| ‘asymmetrically c-commands another instance of itself’ (p. 13). This is why the representation of /u/ (c) requires that |U| self-merges twice. A single application of self-merge would result in the symmetrical configuration (U, U), which lacks asymmetrical c-command. This also means that the two expressions |U| and (U, U) are not contrastive, since i) they are both headless and ii) they contain the same place element. Equally valid representations for symmetrical (U, U) would then be (U, Ø) and (Ø, U). On top of that, it is worth noting that an already asymmetrically c-commanding element may not self-merge again. Otherwise, the generated structure (e.g. *(U, (U, (U, U))) from (13c)) would equally remain as asymmetrical as before, resulting in no extra contrast. Put differently, double-headedness in BEG is naturally ruled out by its fundamental architectural principles.
The merge mechanism has therefore two functions: i) combining different elements to form complex expressions, and ii) assigning a head to such expressions. This is a major advantage over ‘non-structural’ approaches to headedness, which rely on the notion of ‘position’ to determine head status in complex expressions (Kaye et al. 1985, Harris and Lindsey 1995, Charette and Göksel 1996, Backley 2011, Breit 2013,<fnref n="25" /> Faust 2017, among others). That is, there is one position dedicated to the head, and another to the non-head. Problematically, the distribution of these positions is arbitrary; what justifies the assignment of one position to one status (i.e. head or non-head), and why is the other way around excluded (cf. Faust 2017)? In BEG, these problematic questions could not even be formulated, since headedness is defined in purely structural terms.

Element matrices in BEG are also organized in compliance with the architectural principles of Feature Geometry (FG). In that sense, representations such as in (13) are located under hierarchically-organized nodes which altogether shape the substance of segments. Each segment contains three kinds of nodes. Terminal nodes represent matrices of functional primes (in this case, elements<fnref n="26" />). ‘Class’ nodes are groupings of those terminal nodes, carrying values such as place and laryngeal resonance.<fnref n="27" /> The ‘root’ node, by virtue of gathering all class nodes, ‘expresses the coherence of the “melodic” segment as a phonological unit’ (Clements and Hume 1995:18). By combining this architecture with the binary-branching element matrices in (13a) and (13b), we obtain the following representations for unrounded back vowels (skeletal slots above the root nodes are also displayed). The root node put aside, only the place node is required since these segments are exclusively made of place elements (the same goes, of course, for their rounded equivalents).

<footnote n="25">²⁵ As Ulfsbjorninn (2021:11) points out, Breit’s (2013) approach may not be viewed as purely structural, albeit based on merge. In order to correctly derive headedness in a compound set of elements, Breit’s model must ‘presuppose projection of (a) in the *a*-headed structure {{a}, {a,b}}’.</footnote>

<footnote n="26">²⁶ In the standard version of FG (Sagey 1986, Clements & Hume 1995), phonological primes are instanti-ated by features. The use of elements in this model was introduced by Harris & Lindsey (1995).</footnote>

<footnote n="27">²⁷ There is no ‘manner’ node in standard FG (cf. Sagey 1986, McCarthy 1988); rather, all manner features directly associate to the root node. This also goes for Harris & Lindsey’s (1995) element-based version.</footnote>
(14) a. /u/

<figure><img src="image_9.png" /></figure>

b. /ɪ/

<figure><img src="image_10.png" /></figure>

As for consonants, velars and alveolars are associated with symmetrical |U| and |I| respectively, while labials and palatals correspond to asymmetrical (U, (U, Ø)) and (I, (I, Ø)). It follows that labio-velars are composed of both asymmetrical (U, (U, Ø)) and symmetrical |U|.<fnref n="28" /> Also, we have to take into account the |L| element inside the representations of nasal and pre-nasalized velar segments, given in (15). The differences between their structures are detailed and explained below.

(15) a. /ŋʷ/

<figure><img src="image_11.png" /></figure>

b. /ŋ̥g/

<figure><img src="image_12.png" /></figure>

First, we can see that the nasal velar /ŋ/ is made of only one root node (its labial component put aside), whereas the pre-nasalized velar /ŋ̥g/ has two (Piggott 1988, Rosenthall

<footnote n="28">²⁸ This representation is consistent with Ulfsbjorninn's (2021) idea that labio-velars are universally |U|-headed structures.</footnote>
1989, Ioroi 1995). The labialized component in /ŋʷ/ (cf. (15a)) is phonologically trans-
lated as a |U| element, directly attached under a second root node (Root₂). This conforms
to the principles of BEG: At this precise location, |U| is able to c-command another in-
stance of itself (i.e. |U| in Root₁), thereby encoding a labial specification.<fnref n="29" />

Second, in both structures, the |L| element is hosted inside a place node. This requires
some justification, as in FG the feature [nasal] (or, in this case, its ‘equivalent’ |L|) is
generally linked to the root node (cf. McCarthy 1988, Rosenthall 1989, Ioroi 1995).<fnref n="30" /> The
treatment in (15a) and (15b) is in fact motivated by empirical evidence. On one hand,
non-nasal segments in Ngbúgù might carry place elements (e.g. /d/, /k/...), yet it is not
necessarily the case (cf. /ʔ/ and /h/). On the other hand, nasal segments have to be filled
with at least one place element; indeed, never do we find a phonologically placeless seg-
ment that is also nasal (e.g. ‘nasal’ /ʔ/ or /h/?). In other words, the ‘laryngeal’ place of
articulation (which bears no place element) is never instantiated by a nasal segment in
this language. We interpret this fact by claiming the existence of a hierarchical depend-
ency between |L| on one hand, {A, I, U} on the other. That is, the former necessarily needs
support from at least one place element in order to exist inside the sub-segmental struc-
ture.

The two structures in (15) each illustrate one application of this support demanded by
|L|. In (15a), |U| simply merges with it. Note that this treatment is reminiscent of Harris
and Lindsey's (1995) proposition to situate |R| (i.e. the element of coronality) and place
elements under the same 'resonance' (or 'place') node. In (15b), however, |U| and |L| may
not merge since they belong to two different place nodes. Nonetheless, |L| may maintain

<footnote n="29"><sup>29</sup> We thank one of our reviewers for suggesting this structure.</footnote>

<footnote n="30">³⁰ In the original version of FG, the feature [nasal] was associated to the ‘supra-laryngeal’ node (Clements 1985, Sagey 1986).</footnote>
itself by virtue of the association line between |U| and Place₁. As a side effect, the nasal component is also endowed with a velar resonance in its surface form.<fnref n="31" />

## 2.3. THE ‘SEARCH&COPY’ MECHANISM

We saw in section 2.1 that licensing is able to enhance segmental contrasts inside targeted consonantal positions (Harris 1990, 1994, Cyran 2001, 2010). Our proposal to account for the rounding contrast activation between back vowels in Ngbúgù draws from this idea. We hypothesize that licensing may have a beneficial effect, not only for the licensee, but also for the licensor. More precisely, we claim that nuclei may develop additional contrasts through the licensing of preceding onsets (cf. Charette 1991) by extracting melodic material (i.e. elements) out of them.<fnref n="32" /> Under this view, licensing acts as a connection that the nucleus can harness to enrich its own sub-segmental structure.

The idea that a given object may scope inside the overall phonological structure of the word must be attributed to Nasukawa (2016). In his account of (de-)palatalization in Japanese, Nasukawa assumes that an |I| element located inside the nucleus may transfer a

<footnote n="31">³¹ In her study of Bemba (Bantu), Kula (2006) favors another representation for pre-nasalized segments, in which both articulatory components are offered their own constituent. The two constituents are bound together through inter-onset government, and the nasal component is lexically endowed with a nasal |L| element.</footnote>

<footnote n="32">³² We thank one of the anonymous reviewers for suggesting the involvement of a licensing relation. They also proposed that we relied on complexity conditions on consonants to derive the contrast activation, specifically Harris (1994)'s 'Complexity Condition' (CC) and Cyran (2010)'s theory of CSL. It turned out, however, that neither is suitable to the Ngbúgù facts. CC focuses on the interaction between two consonants (in a coda-onset sequence or in a branching onset), in that the governor must be less complex than the governor. Nothing is said about the relative complexity of a vowel in terms of licensing relations, except the fact that it may itself be licensed by another vowel which is prosodically more influent at the level of the foot, i.e. which typically bears stress. But it is irrelevant here, since the Ngbúgù data only feature monosyllabic morphemes, so the only nucleus cannot undergo such influence. In CSL, it is assumed that nuclei are distributed on a 'licensing scale' which determines their potential for licensing their onset: lexically filled nuclei are the best licensors, followed successively by alternating nuclei and empty nuclei. Furthermore, structurally less complex onsets are more easily licensable. This unveils an interesting scenario in which the rounding contrast could be developed only if strong licensors and weak licensees were involved. It would immediately collapse, however, when confronted to the data. On one hand, onsets which allow the rounding contrast exhibit extremely various degrees of complexity (cf. ?_ vs ʔgʷ_). On the other hand, nuclei in our data set are all lexically filled, so they could not be discriminated on the basis of their licensing strength. That being said, we do not completely factor out complexity inside the onset. As we will see in section 3, structural complexity for place of articulation is fundamental to account for the data.</footnote>
copy of itself into the structure of the onset. This is done through the application of a
mechanism he labels ‘SEARCH |H| AND COPY |I| [in the most embedded part of |H|]’ (where
|H| basically is the consonantal position).<fnref n="33" /> His analysis of underlying /ti/ ‘blood’ palatal-
izing into [tɛi] is given in (16) (taken from Nasukawa 2016:13).

(16) NASUKAWA’S ACCOUNT ON PALATALIZATION IN JAPANESE

<figure><img src="image_13.png" /></figure>

We intend to account for the Ngbúgù data by submitting the application of a three-step
phonological process, formally illustrated in (17) (‘α’, ‘β’ and ‘γ’ designate any element
configuration). First, Government-licensing occurs (17a). Second, the place node of the
licensed onset is targeted by the nucleus and its content ‘α’ is copied (17b). This is
achieved with a revised version of Nasukawa’s mechanism, labelled ‘SEARCH&COPY’
(S&C). Third, the copied material ‘αi’ is sent to the place node of the nucleus as a floating

<footnote n="33">³³ Crucially, Nasukawa supports a completely different view of word structure. In his model, named ‘Precedence-free Phonology’ (ibid. 2011, 2012), lateral relations are deleted in favor of structural relations. Constituents do not exist as positive entities anymore; only elements hierarchically ordered in binary branching structures (following the x-bar schema) are the builders of phonological information and interactions.</footnote>
melody (17c). From this point, it may freely associate (or not) to the nucleic structure;
crucially, if this association is possible, then the rounding contrast is activated (a thorough
demonstration is provided in section 3.1).

The originality of S&C lies in the directionality of the effect of the scoping relation,
which is reversed: The nucleus does not transfer a copy of one of its elements into the
onset (in the lines of Nasukawa 2016), but rather incorporates a copy of one element
initially located in the onset.

<figure><img src="image_14.png" /><figcaption>b. S&C (copy in O)</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>c. S&C (transfer in N)</figcaption></figure>

<figure><img src="image_16.png" /></figure>

The representations in (17) illustrate what happens when branching onsets are in-
volved. In this situation, we argue that the nucleus may scope inside both the structure of
the head and that of the complement. Admittedly, it is the head which is licensed by the
nucleus, and not its complement. The latter should, therefore, be out of reach of S&C.
Recall, however, that a given head is granted the ability to govern its complement specif-
ically because it is licensed (see section 2.1). In other words, the complement owes its
existence to the head, which is in turn sustained by the following nucleus. Head-to-com-
plement government can then be viewed as an ‘extension’ of the licensing process. Based
on this, we conclude that the nucleus may extend its scope up to the complement. That
being said, S&C must target the place node of the head first. Heads take priority over complements, since onset licensing occurs before head-to-complement government.

Some concluding observations are in order regarding the nature of S&C. On one hand, it may occur only once, as it is triggered by licensing, which is itself not a repeatable process. Thus, there is no reason to allow several applications of it. On the other hand, it is fundamental to understand S&C as a side effect of the establishment of lateral relations. This process does not occur after the application of onset licensing or government-licensing, but alongside it (i.e. during the formation of phonological domains, as Kaye 1995 understands it). As a consequence, no violation of the Projection Principle is incurred. Section 3 is dedicated to the analysis of the Ngbúgù data, using the three steps shown in (17).

### 3. ANALYSIS OF THE ROUNDING CONTRAST

In the remaining of this paper, we will see how the rounding contrast is activated between back vowels [u] vs [u̯] on one hand, [o] vs [ɔ] on the other. For the sake of conciseness, only representations involving the latter pair are provided.<fnref n="34" /> In particular, we will bring an answer to the three questions below, repeated from (8).

(18) a. Why do ‘oral’ velars activate the rounding contrast?

b. Why do alveolars, palatals, labials and labio-velars block the contrast activation?

c. How can we explain the ambiguous behaviour of simplex vs complex laryngeals and ‘nasal’ velars?

The activation of the rounding contrast in velar contexts (18a) is accounted for in section 3.1. Its failure to take place in alveolar, palatal, labial and labio-velar contexts (18b)

<footnote n="34">³⁴ It is also worth noting that the [o] vs [ɔ] contrast is attested in more contexts. For instance, the sequences *[ɔu] and *[ɔu] are never attested. We cannot precisely figure out why this is the case, but we assume this has to do with a violation of the Obligatory Contour Principle (Leben 1973), as both the consonant and the vowel contain a |U| element. But then we should ask ourselves why other velar contexts such as [ku] or [kw] are attested. Perhaps manner elements inside the onset play a part in this. We leave this problem for further investigation.</footnote>
is the topic of section 3.2. Finally, sections 3.3 and 3.4 focus on the special case of laryngeal and nasal velar contexts (18c). Recall that these do not trigger the contrast when instantiated by simplex onsets; they do, however, when [ɔ] is selected as a complement.

**3.1. ACTIVATION OF THE ROUNDING CONTRAST: ORAL VELARS**

As observed in section 1.2, the rounding contrast is systematically activated in ‘oral’ velar contexts. In total, five are involved: k_ (e.g. [ko] ‘to give’ vs [kɔ] ‘to pick’), g_ (e.g. [go] ‘hunger’ vs [gx] ‘territory’), ɔ_ (e.g. [ɔo] ‘to take a walk’ vs [ɔɛ] ‘to dry’), kvs_ (e.g. [kvsɔ] ‘to stop’ vs [kvsɛ] ‘to open’) and gvs_ (e.g. [gvsɔ] ‘to touch’ vs [gvsɛ] ‘to sweep’).

In (19) is given the representation of underlying /kO/, before and after the application of S&C. Licensing (and S&C) occurs in (19b), where /O/ remains unspecified for rounding. The content |U|, under the place node of the onset, is copied into the place node of the nucleus (the root nodes are not displayed here, since they are irrelevant in this part of the demonstration). Crucially, we argue that the copied melody is phonologically weaker than its original counterpart. This weakness is reflected in the existence of two properties : On one hand, the copied material is a floating melody; on the other, it is unable to establish a direct association with any auto-segmental position (whether it be the place node, the x-slot, or any structural position).

(19) a. /kO/

<figure><img src="image_17.png" /></figure>

b. /kO/ (licensing and S&C)

<figure><img src="image_18.png" /></figure>
At this stage of the derivation, two options are available: either the copied |U| element associates to the structure of N, or it remains afloat (and gets deleted). The first scenario is illustrated in (20a). Given the restrictions outlined above on copied material in general, it appears that the merger of |U| with the inherent (U, A) configuration is the only possible way for it to associate to the nucleic structure (the merging operation is represented by a double-headed arrow). The newly born asymmetrical configuration (U, (U, A)) would then derive rounded /o/.

<figure><img src="image_19.png" /><figcaption>b. /kʊ/ (deletion of copied |U|)</figcaption></figure>

<figure><img src="image_20.png" /></figure>

Alternatively, the copied |U| may also remain afloat, as in (20b), hence deriving un-
rounded /ʊ/. In this case, we claim that |U| is simply deleted. Fundamentally, even though
/ʊ/ (U, A) and /O/ (U, A) share the same phonological structure (compare (19a) and (20b)),
they still are distinct phonological objects. The difference between them is actually one
of form, not substance (following the terminology found in Hjelmslev 1943): /O/ is indeed
involved in no paradigmatic relationship with /o/, unlike /ʊ/. The concomitance of these
two possibilities at one nucleic position, association (through merge) or non-association
of the copied |U| element, is what nourishes the contrast between rounded /o/ and un-
rounded /ʊ/.
It is fundamental to see this potential association of copied |U| as entirely free, i.e.
unconditioned in any way. Otherwise, it would be impossible to derive the lexical alter-
nation between [o] and []. The justification for this move relies on typological evidence:
Some languages do have segments which may freely associate to structural positions. The
schwa /ə/ in French is a perfect illustration of this phenomenon: Non-contrastive alterna-
tions may arise due to its (non-)realization, as in the pairs of forms [ʃəmɛ̃]~[ʃ_mɛ̃] ‘path’,
[səкɛ̃g]~[s_кɛ̃g] ‘syringe’, [ʒəle]~[ʒ_le] ‘frozen’, etc.

That being said, this analogy raises an important question: why would the free associ-
ation of |U| lead to a phonemic contrast in Ngbúgù, whereas that of /ə/ in French would
not? We propose that the answer lies in the relative integrity of the nucleic structure as
permitted by the relevant alternations in these two languages: in French, this structure is
entirely preserved, whereas in Ngbúgù it is not. In the former, the underlying representa-
tion of /ə/ remains intact regardless of whether it surfaces, while in the latter, it undergoes
modification. As previously noted, the association of |U| necessitates its merger with the
(U, A) configuration, thereby yielding an asymmetrical structure (U, (U, A)), as shown in
(20a). If, however, |U| remains unassociated (and gets deleted), the melodic structure re-
tains its symmetry, as illustrated in (20b). Crucially, within the BEG framework, asym-
metry constitutes a contrastive property between segments. Consequently, the only pos-
sible outcome of this free (non-)association in Ngbúgù is the emergence of a new phone-
mic contrast.

In sum, S&C provides the nucleus with new material, which can be exploited (or not)
in order to build extra contrast that is not lexically available from the phonemic inventory
of Ngbúgù.<fnref n="35" /> Representations for the remaining contexts are not given. The analysis of

<footnote n="35">³⁵ One reviewer suggests a very interesting alternative. In their analysis, /o/ and /r/ are portrayed as distinct phonological objects from the very beginning of the derivation (i.e. when licensing occurs, as in (17a) and (19b)). This approach, consequently, does not acknowledge the existence of a contrast activation, but follows more familiar thinking by favoring a ‘neutralization’ solution. The core proposition is that the structure of /o/ could be defective, in that its head |U| needs to be bi-positional. Velar onsets provide the sufficient material for its repair: Their |U| element, which inherently occupies the place node of O, also acts as a head for the (U, (U, A)) configuration inside the place node of N, by linking to it. As for /r/, since it is lexically</footnote>
the other simplex contexts g_ and k_ exactly conforms to (19) and (20). As for complex
kobil and gbil, the complement /b/ plays no role here; the structure of the head alone suf-
fices to account for the contrast activation (see section 2.3 for more details). We will,
however, start to acknowledge its significance in section 3.3.

## 3.2. ILLICIT CONFIGURATIONS: LABIALS, ALVEOLARS, PALATALS, LABIO-VELARS

This section focuses on the set of consonantal contexts which never activate the rounding
contrast (cf. question (18b)). Four places of articulation are concerned, in their simplex
as well as their branching form (i.e. which display [k] as a complement): labials (e.g.
[po]~[px] ‘to talk’, [vo]~[vx] ‘to pinch by scratching’, [pκx] ‘egg’, [fκx] ‘to rub’), alveo-
lars (e.g. [to]~[tx] ‘to originate’, [do]~[dx] ‘to turn’, [tκx] ‘to wipe’ [sκx] ‘to tear’), palatals
(e.g. [tʃo]~[tʃx] ‘to taste good’, [ʃκx] ‘to tighten’) and labio-velars (e.g. [kpo] ‘to grow up’,
[kpɔo] ‘repeatedly’).

Expectedly, based on the representations in elements of these places of articulation (cf.
sections 2.2.1 and 2.2.2), the outcome of S&C (i.e. the copy of extra material into the
place node of the nucleus) cannot yield any contrast activation. On one hand, if the float-
ing copied material does not associate, it gets deleted, deriving symmetrical (U, A) (as in
(20b); see section 3.1). On the other hand, if its associates (through merge) to the nucleic
structure, then an illicit structure is formed, deficient in either one of the two following
ways (or even both): i) it is double-headed; ii) its surface form is not attested in Ngbúgù.

The representations in (21) illustrate these two undesirable outcomes. In labial con-
texts (21a) (e.g. [po]~[px] ‘to talk’), the place node of the onset hosts an asymmetrical
(U, (U, Ø)) configuration. During onset licensing, S&C applies and the copied content
merges with that of the nucleus (U, A). This yields the expression *((U, (U, Ø)) ((U, A))).

<footnote>headless, nothing happens. This approach deserves credit for soliciting less heavy phonological machinery. Nevertheless, we believe it fails to fully capture the relevant data. In short, it appears to incorrectly predict the absence of contrast between back vowels following most complex onsets (i.e. onsets that select /k/ as a complement). Given that /k/ contains a |U| element (which is also necessary in this approach to predict contrasts such as [kɔ] ‘to take a walk’ vs [kʊ] ‘to dry’), there is no clear reason why the contrast should not be maintained in forms like [pκy] ‘egg’ or [tκy] ‘to wipe’.</footnote>
Problematically, the place node of the nucleus ends up with an asymmetrically c-commanding structure whose head (U, (U, Ø)) is itself asymmetrical (as it also contains an asymmetrically c-commanding |U| element). In other words, it is double-headed.

In alveolar contexts (21b) (e.g. [to]~[tɛ] ‘to originate’), S&C provides the nucleus with an |I| element, which merges with (U, A). The generated configuration *(I, (U, A)) is illicit for two reasons. First, it violates one of the core principles of BEG: the head |I| does not asymmetrically c-command another instance of itself. Second, the simultaneous presence of the three place elements {I, U, A} inside the nucleus cannot be tolerated in Ngbúgù. The corresponding surface form would be a front rounded vowel, such as [ø], which is not attested in this language.

<figure><img src="image_21.png" /><figcaption>(21) a. /pO/ ‘to talk’ (*double-headedness)</figcaption></figure>

<figure><img src="image_22.png" /><figcaption>b. /tO/ ‘to originate’ (*[tø])</figcaption></figure>

<figure><img src="image_23.png" /></figure>

We assume that the consecutive applications of S&C and merge in (21a) and (21b) lead to a derivational crash. From this point, the phonology carries out a fixing strategy which deletes the copied material brought by S&C (i.e. (U, (U, Ø)) in (21a) and |I| in (21b)). Subsequently, only symmetrical (U, A) remains inside the nucleus, and no rounding contrast can be developed; /O/ remains underspecified, and rounded [o] and unrounded [ɣ] stay in free variation.
The absence of a contrast activation in palatal and labio-velar contexts goes without saying. Labio-velars are partly labial, so they behave as such (as far as the rounding contrast activation is concerned, at least). As for palatals, they stack up the undesirable properties of both labials and alveolars: The representation of their place of articulation (I, (I, Ø)) is asymmetrical and contains the |I| element. Finally, branching configurations do not provide adequate conditions for the rounding contrast activation either. Indeed, the place node of the complement [k] cannot be selected by S&C, as the head must be taken into consideration first.

**3.3. EMPTY PLACE NODES: LARYNGEALS**

How can we explain the divergent behavior of laryngeal onsets? Recall that, while simplex ?_ never allows the rounding contrast to occur (e.g. [ʔo]~[ʔɔ] ‘to shout’) in the succeeding nucleus, its branching equivalent ʔk_ does (e.g. [ʔko] ‘to whistle’ vs [ʔkɔ] ‘to scold’). It is important to remember that laryngeals are phonologically unspecified for place of articulation; in other words, they carry no place element. In accordance with the formal mechanisms posited so far, nothing is thus predicted to happen. The lexical structure of laryngeal /ʔ/ has no material inside its place node to be targeted and copied.

The situation is different for branching ʔk_, which displays [k] as a complement. Recall that, in the previous section, the place node of the complement could not be targeted by S&C. This is due to the requirement that the head is checked first. Yet, there is no material inside the place node of laryngeals. S&C may therefore copy the |U| element inside the complement, which might merge with the nucleic configuration (U, A). If it does, asymmetrical (U, (U, A)) is generated, as shown in the representation of [ʔko] ‘to whistle’ in (22). The derivation proceeds exactly like in velar contexts (for further details about the contrastive alternation between [o] and [ɣ], see section 3.1).
(22) /ʔkɔ/ ‘to whistle’

<figure><img src="image_24.png" /></figure>

Before we get to the next section, some comments on the status of /ʔk/ as a branching onset are in order. Following Harris’ (1994) Complexity Condition (cf. fn. 29), it should be impossible that /k/ acts as a dependent of /ʔ/ since the former is segmentally more complex than the latter. If so, word-initial */ʔk/ would simply be ill-formed, as it generates an upward sonority slope. One convenient way to get around this problem could be to state that /ʔ/ is extra-syllabic in Ngbúgù, while /k/ behaves as a simplex onset in this case. Nevertheless, we can think of no external argument which sustains this idea. In any case, this matter is orthogonal to the present analysis, since either treatment of /ʔk/ would equally yield contrast activation. If /ʔ/ were somehow rejected the possibility to select /k/ as a complement, the place node of /k/ (as a simplex onset) would still be the only available target for S&C.

### 3.4. THE INTERACTION BETWEEN |L| AND |U|: NASAL AND PRE-NASALIZED VELARS

Nasal velar contexts exhibit the same hybrid behavior as laryngeals towards back vowels: simplex contexts ɣʷ_ (e.g. [ŋʷo] ‘to kill’) and ŋg_ (e.g. [ŋgɣ] ‘breast’) do not activate the rounding contrast, whereas branching ŋgk_ does (e.g. [ŋgko] ‘to scratch’ vs [ŋgky] ‘to make a detour’).

We will first focus on simplex onsets, whose representations are given in (23). As it was established in section 2.2.2, nasal and pre-nasalized velars both carry the |L| and |U|
elements. The representations of the two segments only differ in the distribution of these
elements in their structure. In nasal velars (23a), |L| and |U| merge to yield the configura-
tion (L, U) inside a unique place node. In pre-nasalized velars (23b), they are scattered
across two place nodes (Place₁ and Place₂). Each place node is associated with its own
root node (Root₁ and Root₂), and the entire configuration is hosted under one skeletal slot.

<figure><img src="image_25.png" /><figcaption>b. /朋gO/ ‘breast’</figcaption></figure>

<figure><img src="image_26.png" /></figure>

In (23a) as in (23b), it is the |L| element which prevents the activation of the rounding
contrast. In (23a), the (L, U) configuration is copied and merge with nucleic (U, A), yield-
ing the illicit expression *((L, U), (U, A)). The outcome of S&C and merge inside the
nucleic structure in (23b) asks for further clarification. Two points need to be addressed.

On one hand, the two place nodes inside the onset (Place₁ and Place₂) are simultane-
ously targeted by S&C. This treatment seems to contradict what we have established so
far. Recall that, in contexts containing two place nodes (previously examined in section
3.2), only one of them could be selected. However, the situation currently at hand is dif-
ferent. In a branching context, it is impossible for S&C to target both the place node of
the head and that of the complement, since there is a governing relation that holds between
them. The former takes priority over the latter and its structure must therefore be checked
first by the nucleus. In (23), even though /্g/ has two root nodes, the onset is not branch-
ing. Thus, there is no head nor complement positions to be distinguished within it; the
only lateral relation that holds is licensing. Therefore, the entire structure of /্g/ is avail-
able for checking, and S&C targets whatever place material it can find.

On the other hand, even though |L| and |U| are not merged inside the onset in (23b),
their copy is sent as the merged configuration (L, U) to the nucleus. This is consistent
with the idea that S&C is a one-time mechanism. Suggesting that the copies of |L| and |U|
were incorporated inside the nucleus as separate objects would entail that S&C actually
occurs twice.

In (23a) as in (23b), the reason why the rounding contrast is not activated is quite
reminiscent of what happens in (21a) (i.e. in labial contexts): the nucleic configurations
are double-headed. Recall that headedness is defined in BEG as asymmetrical c-com-
mand. Since (L, U) asymmetrically c-commands |U| and |A| (located under the (U, A)
configuration), both |L| and |U| have head status. Additionally, the expression
*((L, U) (U, A)) hosts the |L| element, which is not tolerated inside Ngbúgù nuclei. In-
deed, no nasal vowel is attested in this language. As a consequence, it is impossible for
back vowels to develop a rounding contrast in this context.

We will now cover the last remaining context: branching pre-nasalized velars ্gk_. As
was said before, laryngeal and pre-nasalized velar contexts pattern in the exact same way:
although simplex onsets do not allow the rounding contrast (cf. ?_ and ্g_), their branch-
ing equivalents do (cf. ?k_ and ্gk_). In section 3.3, we straightforwardly allocated the
divergent behavior of laryngeal contexts to the presence or absence of [k] as a comple-
ment. We will presently see that [k] is also involved in the case of ্gk_, though in a dif-
ferent fashion. The relevant representation is given in (24).
(24) /্ŋgɔ/ ‘to scratch’

<figure><img src="image_27.png" /></figure>

Before discussing the application and the outcome of S&C and merge, a clarification on the formation of the structure of the onset is required. As we can see, there is a (U, U) configuration dominated by both the place node proper to the plosive component of the head /্ŋg/ (i.e. Place₂) and the single place node of the complement /к/ (i.e. Place₃). Here, the two |U| elements which were originally lodged in these place nodes have merged. We legitimate this move by relying on two theoretical arguments. First, the Obligatory Contour Principle (Leben 1973), which disfavors the contiguity of two identical objects on the same auto-segmental tier, is satisfied. Second, there is no reason for the phonology to prevent this operation. According to BEG, (U, U) is indeed equal to |U| in terms of lexical contrast (see section 2.2.2). Velarity is therefore preserved for the entire /্ŋg/ cluster.<fnref n="36" />

<footnote n="36">³⁶ This merge operation is seemingly identical to other principles used in FG, such as Clements' (1985:240) Shared Feature Convention (SFC) and Rosenthall's (1989:68) Inverse Contour Condition (ICC). These are also responsible for the formation of many-to-one relations between auto-segments. We do not claim, nevertheless, that the merged (U, U) configuration in (24) is the outcome of either of these. SFC and ICC were posited to account for assimilation processes, such as gemination and nasal-plosive homorganicity. They are thus irrelevant to the present study.</footnote>
Government-licensing occurs and S&C targets both place nodes inside the head x₁
(Place₁ and Place₂), like in (23b). The comparison stops here, however, since the copied
material contains the |L| element under Place₁ as well as the above-mentioned (U, U)
under Place₂. Both of these elemental configurations merge to create the virtual
*(L, (U, U)) configuration. At this stage, it is essential to point out that this copy of
merged elements is structurally ill-formed: |L| does not asymmetrically c-command an-
other instantiation of itself.

That being said, we claim that S&C is unable to proceed further, unless the nucleus is
provided with a structurally licit configuration. To achieve this, the problematic |L| ele-
ment is simply filtered out. Subsequently, only (U, U) is sent into the nucleus. In case it
merges with (U, A) the ((U, U) (U, A)) configuration is generated. Now, considering the
fact that (U, U) is lexically equivalent to |U|, rounded /o/ may be derived. The rounding
contrast in branching pre-nasalized velar onsets can therefore be activated.

CONCLUSION

In this paper, we have provided an explanation for the contextual rounding contrast be-
tween the two pairs of back vowels [o] vs [ɔ] and [u] vs [ʊ] in Ngbúgù. This contrast is
only attested in seven consonantal contexts: k_, g_, ɔ_, kɔ_, gɔ_ ɔk_ and ɒgɔ_, thereby
warranting the hypothesis of a contrast activation (rather than a contrast neutralization).
Crucially, the presence of a velar component is a necessary condition for the activation of
this contrast. Therefore, labial, alveolar, palatal and labio-velar contexts never allow it. In
addition, while simplex laryngeals (?_), nasal and pre-nasalized velars (η_, ɒg_) forbid the
contrast as well, their branching configuration ɔk_ and ɒgɔ_ do not.

Relying on the frameworks of Government Phonology, Element Theory and Feature
Geometry, we suggested the consecutive application of three phonological mechanisms:
i) onset licensing (as well as government-licensing, and head-to-complement government
in case of branching onsets); ii) S&C, a scoping mechanism that allows the nucleus to
search and copy material inside the place node of the licensee; iii) the transfer of that
copied material into the place node of the licensor, as a floating melody. Crucially, that
floating melody may be exploited by the nucleus to enhance its own contrastive power.
When applying these tools to the data, we obtained the following results.

‘Oral’ velars (i.e. velars with no nasal component) activate the rounding contrast be-
cause the place node of the onset contains a unique |U| element. Once |U| merges with the
place configurations |U| or (U, A) inside the nucleus, a new asymmetrical (i.e. headed)
configuration (U, (U, A)) or (U, (U, Ø)) is generated. This derives rounded vowels /o/ and
/u/, respectively. The formation of their lexically unrounded equivalent /ɜ/ and /u/ is then
achieved by the non-association (and the deletion) of the copied melodic material inside
the nucleus.

However, alveolar, palatal, labial and labio-velar contexts may not activate the round-
ing contrast, since the content of their place node is inadequate. When the latter merges
with that of the nucleus, an illicit configuration is generated. The derivation then crashes,
and the following back vowel /U/ or /O/ remains unspecified for rounding. Also, when
the onset is branching, the nucleus cannot exploit the velar complement /k/; the place
node of the head must be targeted in priority.

The treatment of laryngeals and nasal velars turned out to be more complex. The place
node of laryngeal segments is empty, so no material can be extracted out of it by S&C.
When the laryngeal onset is branching, however, the |U| element of its complement /k/
may be targeted by S&C. As for simplex ‘nasal’ velars, the merging of their |L| element
with the nucleic structure generates once more an illicit configuration. When they happen
to be in a branching configuration, however, the |U| element inside the complement disa-
bles |L| for structural reasons.

Clearly, the existence of S&C sheds light on a very interesting fact: It is possible for
phonological contrasts to develop during the formation of phonological domains. In other
words, inventories of phonemes may be (partly) built by such domains, at least from a
synchronic perspective.
Further work will have to investigate other interesting vocalic distributions occurring
in Ngbúgù. We introduce two of them. First, other data we collected suggest that the con-
trast between front and central vowels is also absent in some contexts. For example, [i]
and [ə] never appear after a labial or a palatal consonant. Similarly, [i] is rarely attested
in alveolar contexts. Second, the rounded back vowels [u] and [o] might freely alternate
with a glide-vowel sequence ([wo] and [wu]), but only in velar and branching laryngeal
contexts.

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ABSTRACT IN FRENCH

La langue ngbúgù (groupe banda, famille oubanguienne ; République centrafricaine) manifeste un contraste contextuel entre voyelles arrondies et non-arrondies ; les deux contrastes [o] vs [x] et [u] vs [w] ne sont attestés que dans sept contextes : k_, g_, kʷ, gʷ, ʷ, ʔk_ et ʔgʷ. Étant donné la distribution très limitée de ce contraste, nous suggérons qu’il est activé dans ces contextes, plutôt que neutralisé ailleurs. En nous appuyant sur les cadres de la Théorie des Éléments (Kaye et al. 1985, 1990, Backley 2011), de la Phonologie du Gouvernement (Kaye 1990, Kaye et al. 1990, Charette 1990, 1991), et de la Géométrie des Traits (Clements 1985, Sagey 1986, Clements et Hume 1995) appliquée aux éléments (Harris et Lindsey 1995, Ulfsbjorninn 2021), nous proposons une analyse représentationnelle dans laquelle l’élément |U| est responsable de cette activation.

**Mots-clés** : ngbúgù (banda, oubanguien), contraste d’arrondissement, Phonologie du Gouvernement, Théorie des Éléments, Géométrie des Traits
A LATENT PHONEMIC SPLIT – DISCUSSION WITH FABIAN ZUK
(CNRS—LANGAGE, LANGUES ET CULTURES D'AFRIQUE)

Zuk, Fabian. 2025. A Latent Phonemic Split – Discussion in Althabégoïty, Galla; Vancaeyzeele, Charles (authors). “Rounding Contrast Activation in Ngbúgù: Licensing and Sub-segmental interactions”. *Radical: A Journal of Phonology*, 7, 32-86.

PERSPECTIVE

Ngbúgù shows a conditioned distribution of phonemic contrasts. The authors are ambitious in their effort to turn a typical *neutralisation* analysis on its head, arguing instead for an *activation of contrasts* within a limited phonological environment. Descriptively the rounded back vowel /u/, /o/ alternate freely with the unrounded back vowels /u/, /ɔ/ in all monosyllables without a dorsal onset, e.g. *tu* ~ *tui* ‘ear’, *to* ~ *tɔ* ‘rotv’, etc. These rounded and unrounded vowel pairs are only contrastive in a limited number of environments, which, descriptively, we can simplify to just two:

① after a dorsal obstruent: /k, g, ɔ/, e.g. ku ‘jump’ vs kuw ‘drip’, or

② after /k/ when proceeded by a dorsal or glottal stop, e.g. kuɔ ‘stop’ vs kuɔ́ ‘pierce’.

Within these contexts, the data reveal that forms which *always* surface with the rounded vowels /u/ and /o/ are optionally accompanied by a bilabial onglide /w/ after a dorsal onset: e.g. *kwu* ‘jump’, *kwo* ‘stop’, *ngwú* ‘water’, etc. Inversely, forms which *always* surface with unrounded /u/ (such as *ku* ‘drip’) and /ɔ/ (such as *kɔ* ‘pick’) *never* surface with said onglide demonstrating perfect complementary distribution. I believe the key to understanding “contrast activation” in Ngbúgù lies here in the fact that the bilabial glide
/w/ and the unrounded vowels can never co-occur. In arguing for “activation” in synchrony, I believe the authors have inadvertently observed the early stages of what in historical linguists is called a *secondary split*, that is the appearance of a new phoneme, due to a change in previously allophonic variation, notably caused by the merger of conditioning environments elsewhere in the system (cf. Hoenigswald 1960; Campbell 2020: 21).

In (1) and (2) I have aggregated data drawn from Althabégoïty (2024) along with complementary Ngbúgù data from Boyeldieu (1989), Touguele (2008) and Olson (2022) and have separated forms according to whether they surface with a rounded vowel, an unrounded vowel or whether either realisation is possible. As recognized by the authors, previous descriptions of Ngbúgù have transcribed Althabégoïty’s informants’ [w] as /u/.

<table><thead><tr><th>(1)</th><th>Ngbúgù<br>(Althabégoïty)</th><th>Ngbúgù<br>(other)</th><th>Northern Gbaga<br>(Nougayrol 1997)</th><th>Banda-Banda<br>(Éboué 1918)</th></tr></thead><tbody><tr><td colspan="5" style="text-align: center; font-weight: bold;">source</td></tr><tr><td colspan="5" style="text-align: left; font-weight: bold;">[u]</td></tr><tr><td>a.</td><td>kwu, ku</td><td>'trapN'</td><td>kwu</td><td>B</td></tr><tr><td></td><td>kwu, ku</td><td>'wound'</td><td>-</td><td>-</td></tr><tr><td>b.</td><td>gwu, gu</td><td>'grow'</td><td>gwu</td><td>B</td></tr><tr><td>c.</td><td>ŋgwú, ngú</td><td>'water'</td><td>ngwú</td><td>B</td></tr><tr><td>d.</td><td>ŋwu</td><td>'see'</td><td>ŋwu</td><td>B</td></tr><tr><td colspan="5" style="text-align: left; font-weight: bold;">[u]</td></tr><tr><td>e.</td><td>kw</td><td>'drip'</td><td>ku</td><td>B</td></tr><tr><td>f.</td><td>kw</td><td>'thigh'</td><td>ku</td><td>O</td></tr><tr><td></td><td></td><td></td><td>kū</td><td>B</td></tr><tr><td></td><td>kú</td><td>'bug'</td><td>kú</td><td>B</td></tr><tr><td>g.</td><td>gw</td><td>'leave'</td><td>gu</td><td>B</td></tr><tr><td>h.</td><td>gw</td><td>'insult'</td><td></td><td></td></tr><tr><td colspan="5" style="text-align: left; font-weight: bold;">[u ~ w]</td></tr><tr><td>i.</td><td>tu, tw</td><td>'ear'</td><td>tū</td><td>O</td></tr><tr><td></td><td></td><td></td><td>tū</td><td>B</td></tr><tr><td>j.</td><td>[ʃu], [tʃu]</td><td>'die'</td><td>cu</td><td>B</td></tr><tr><td></td><td></td><td></td><td>tʃù</td><td>T</td></tr><tr><td>k.</td><td>pu, pw</td><td>'search'</td><td>pu</td><td>B</td></tr><tr><td>l.</td><td>bu, bw</td><td>'blacken'</td><td>bu</td><td>B</td></tr><tr><td>m.</td><td>fu, fw</td><td>'be good'</td><td>fu</td><td>B</td></tr><tr><td>n.</td><td>ʃu, ʃw</td><td>'bitter'</td><td>ʃu</td><td>B</td></tr><tr><td>p.</td><td>ʒu, ʒw</td><td>'burn'</td><td>ʃɔ</td><td>B</td></tr></tbody></table>
Previous descriptions of Ngbúgù have also included an additional round vowel phoneme /ɔ/ there where Althabégoïty transcribes [ɣ]. I believe Althabégoïty’s keen ear has detected an ongoing and generalized surface delabialization of the back vowels, which entirely accounts for the free variation seen in tu ~ tuu ‘ear’ (1i), po ~ pr ‘talk’ (1v), etc. More critically, however, are those environments where rounded and unrounded vowels are contrastive. Olson (2022) has simply dealt with this distribution by treating both /o/ and /ɔ/ as distinct phonemes which are in the process of undergoing a merger. Olson (2022: 13) has also documented an addition back rounded phoneme /ʊ/ which Boyeldieu & Cloarec-Heiss (2001: 199, 202-203) reconstruct as *ʊ for Proto-Banda. Relevant to this discussion, Olson’s /ʊ/ surfaces as [wo] in Althabégoïty (2024)’s data.<fnref n="37" />

<table><thead><tr><th>(2)</th><th>Ngbúgù<br>(Althabégoïty)</th><th>Ngbúgù<br>(other)</th><th>Northern Gbaga<br>(Nougavrol 1997)</th><th>Banda-Banda<br>(Éboué 1918)</th></tr></thead><tbody><tr><td colspan="5" style="text-align: center; font-weight: bold;">[o]</td></tr><tr><td colspan="5" style="text-align: center;">source</td></tr><tr><td>a.</td><td>kwo,<br>kwo,<br>ko</td><td>kwo<br>kwɔ<br>kʊ</td><td>B<br>B<br>O</td><td>ko<br>ko<br>ògò</td><td>ko<br>ko<br>gogo</td></tr><tr><td>b.</td><td>gwo,<br>gwo</td><td>gɔ<br>gwɔ<br>gò</td><td>O<br>B<br>T</td><td>ògò</td><td>‘hunger’</td></tr><tr><td>c.</td><td>ŋkwo,<br>ŋko</td><td>ŋwu,<br>ŋwɔ</td><td>B</td><td>ŋwu</td><td>‘blow’</td></tr><tr><td>d.</td><td>ŋgbwo,<br>ŋgɔ</td><td>ŋgbwɔ<br>ŋgkɔ</td><td>B<br>O</td><td>nguru</td><td>‘scratch’</td></tr><tr><td>e.</td><td>kwo,<br>kwo</td><td>wɔ<br>kwɔ</td><td>B</td><td>ri</td><td>‘walk’</td></tr><tr><td>f.</td><td>kwo,<br>kwo</td><td>kwo<br>kwɔ</td><td>B</td><td>-</td><td>-</td></tr><tr><td>g.</td><td>ŋwo<br>ŋwo</td><td>ŋwɔ<br>ŋwɔ</td><td>B</td><td>ŋwo</td><td>‘kill’</td></tr><tr><td colspan="5" style="text-align: center; font-weight: bold;">[ɔ]</td></tr><tr><td>h.</td><td>kɔ</td><td>kɔ</td><td>B</td><td>ko</td><td>‘prendre’</td></tr><tr><td>i.</td><td>kɔ</td><td>kɔ</td><td>B</td><td>-kɔʃɛ</td><td>‘male’</td></tr><tr><td>j.</td><td>kɔ</td><td>kɔ</td><td>O</td><td>kɔkɔ</td><td>‘termites’</td></tr><tr><td>k.</td><td>gɔ</td><td>gɔ</td><td>B<br>‘village’</td><td>ɔgɔ</td><td>‘land’</td></tr><tr><td>l.</td><td>ŋkɔ</td><td>ŋkɔ</td><td>T</td><td>-</td><td>-</td></tr></tbody></table>

<footnote n="37">³⁷ Also note, the lack of either the high vowels [u] or [w] after /Cv/ suggesting that forms like tɔv ‘wipe’ (2r) may result from the lowering of earlier *Cv sequences.</footnote>
<table><tr><td>m.</td><td>ŋgɔ̃</td><td>'detour'</td><td>ɔ̃</td><td>B</td><td>ro</td><td>'pass'</td><td>ro</td><td>'bypass'</td></tr><tr><td>n.</td><td>ɔ̃</td><td>'dryv'</td><td>ɔ̃</td><td>B</td><td>ɔ̃</td><td>'dryv'</td><td>ɔ̃</td><td>'dryv'</td></tr><tr><td>o.</td><td>kɔ̃</td><td>'pierce'</td><td>krɔ</td><td>B</td><td>kɔ̃</td><td>'pierce'</td><td>-</td><td>-</td></tr><tr><td>p.</td><td>ŋgɔ̃</td><td>'breast'</td><td>ngɔ̃</td><td>B</td><td>ɔ̃</td><td>'breast'</td><td>ongo</td><td>'breast'</td></tr><tr><td>q.</td><td>ŋgɔ̃tɔ̃</td><td>'chicken'</td><td>ngɔ̃tɔ̃</td><td>B</td><td>ngātɔ̃</td><td>'chicken'</td><td>ngato</td><td>'chicken'</td></tr><tr><td>r.</td><td>tɔ̃</td><td>'wipe'</td><td>tɔ̃</td><td>B</td><td>-</td><td>-</td><td>tulu</td><td>'wipe'</td></tr><tr><td>s.</td><td>sɔ̃</td><td>'tear'</td><td>sɔ̃</td><td>B</td><td>suru,<br>swuru</td><td>'tear'</td><td>suru</td><td>'tear'</td></tr><tr><td>t.</td><td>ʃɔ̃</td><td>'tighten'</td><td>ʃχɔ̃</td><td>T</td><td>-</td><td>-</td><td>-</td><td>-</td></tr><tr><td>u.</td><td>pɔ̃</td><td>'egg'</td><td>pɔ̃</td><td>B</td><td>pārā</td><td>'egg'</td><td>pre</td><td>'egg'</td></tr><tr><td colspan="9">[o ~ ɔ]</td></tr><tr><td>v.</td><td>po, pɔ̃</td><td>'talkv'</td><td>pɔ</td><td>B</td><td>-</td><td>-</td><td>pa</td><td>'talkv'</td></tr><tr><td>w.</td><td>bo, bɔ̃</td><td>'termite'</td><td>bɔ</td><td>B</td><td>àbɔ̃bɔ̃</td><td>'termite'</td><td>obo</td><td>'termite'</td></tr><tr><td>x.</td><td>to, tɔ̃</td><td>'marry'</td><td>tɔ</td><td>O</td><td>to</td><td>'marry'</td><td>to</td><td>'marry'</td></tr><tr><td>y.</td><td>vo, vɔ̃</td><td>'pinchv'</td><td>vɔ</td><td>B</td><td>pɔ</td><td>'pinchv'</td><td>vo</td><td>'pinchv'</td></tr><tr><td>z.</td><td>fo, fɔ̃</td><td>'rotv'</td><td>fɔ̃</td><td>B</td><td>fu</td><td>'rotv'</td><td>ufu</td><td>'rotten'</td></tr><tr><td>aa.</td><td>mo</td><td>'laughv'</td><td>mɔ</td><td>B</td><td>mɔ</td><td>'laughv'</td><td>mo</td><td>'mock'</td></tr></table>

## THE SECONDARY SPLIT

While I shall take no stance on the reconstruction of Proto-Banda, comparison of Ngbúgù with related Northern Gbaga (Nougayrol 1997) and more distant Banda Banda (Éboué 1918) suggests, that Althabégoïty's observed [w] and [r] are (relatively) recent realisations of earlier Ngbúgù back rounded vowels.<fnref n="38" /> This delabialization is optional when /u/ and /o/ are preceded by non-dorsal stops or fricatives as in /fu ~ fu/ 'bitter' (1n) or /bo ~ br/ 'termite' (2w). Here, lenition has pushed for the delabialisation of /u/ and /o/ so that [w] and [r] have become free variants of /u/ and /o/, characterized by the loss of /U/’s headedness within the nucleus (cf. Harris 2005). Critically however, delabialized [w] and [r] are the **only** allophones permitted when the onset of a monosyllabic morpheme contains a non-labialized dorsal consonant, e.g. ku 'drip' (1e), gu 'leave' (1g), kr 'pick' (2h), etc.

<footnote n="38">³⁸ The authors (p.c.) have expressed their concerns with treating Banda Banda as representative of some ancient state of Ubangi. Phylogenetic difficulties aside, Éboué (1918)'s transcription provide relevant time depth for understanding the Banda languages, including Ngbúgù.</footnote>
In other words, /o/ and /u/ have entirely delabialized in post-velar environments, fully matching their velar onsets in their non-headed-|U| specification.

On the contrary, /u/ and /o/ do not undergo synchronic delabialization when preceded by a bilabial glide /w/ |U|, generally as part of a complex onset, e.g., gwu ‘grow’ (1b), ngwu ‘see’ (1d), gwo ‘hunger’ (2b), ngwo ‘kill’ (2g), ?gwo ‘whistle’ (2c), nggwo ‘scratch’(2d), etc. In this specific phonological environment, /u/ and /o/ preserve (or re-acquire) full |U|-headed values [o] and [u]. Essentially, inherited /o/ and /u/ are reinforced when supported by the bilabial glide in onset and reduced elsewhere. The SEARCH & COPY mechanism proposed by the authors may well be responsible for the incorporation of |U| from the onset into the following nucleus.

The resulting surface values can therefore be explained as the consequence of two competing forces: **LENITION** which targets underlying |U|, pushing for the loss of its headed status, and **ASSIMILATION** whereby the preceding /w/, bleeds **LENITION** of its ability to act upon |U|, or alternatively restores the |U|-headedness of /u/ and /o/, masking the effects of **LENITION**. The result is a four-vowel surface contrast as seen in (3).

(3) Vowel Specifications

<table><thead><tr><th></th><th>|U|</th><th>|U+U|</th></tr></thead><tbody><tr><td>Ø</td><td>w</td><td>u</td></tr><tr><td>|A|</td><td>y</td><td>o</td></tr></tbody></table>

This analysis of course requires us to consider /w/ in (1a–d) and (2a–g) as part of the underlying phonological form, which is unproblematic since both Touguele (2008: 60, 71) and Althabégoïty (2024) recognize /w/ as a consonantal phoneme of Ngbúgù and as the surface realisation of /u/ in hiatus, both of which are represented by the element |U|.$^{39}$

<footnote>$^{39}$ Ngbúgù /w/ appears in the same position in Boyeldieu (1989) and Althabégoïty (2024) with few exceptions. Forms such as ‘whistle’, Alt. ?gwo vs Boy. ?wkwɔ ‘whistle’ ‘whistle’ (2c) suggest</footnote>
In fact, when Ngbúgù post-consonantal /w/ is juxtaposed to the related Northern Gbaga language, one finds that probable cognates instead contain an additional rounded vowel (/u/ or /o/) whose transphonologisation may account for a portion of the Ngbúgù /w/, though further comparative discussion is beyond the scope of this response and orthogonal to the synchronic analysis proposed here.

(4) Comparison of Ngbúgù and related Northern Gbaga

<table><thead><tr><th></th><th>úngú</th><th>ókú</th><th>ʔuru</th><th>nguru</th><th>ògò</th></tr></thead><tbody><tr><th>Northern Gbaga</th><td>‘water’</td><td>‘trap<sub>N</sub>’</td><td>‘blow’</td><td>‘scratch’</td><td>‘hunger’</td></tr><tr><th>Ngbúgù</th><td>ŋgwú</td><td>kwú</td><td>ʔkʷu</td><td>ŋgkʷo</td><td>gwò</td></tr><tr><th></th><td>‘water’</td><td>‘trap’</td><td>‘whistle’</td><td>‘scratch’</td><td>‘hunger’</td></tr></tbody></table>

Whether one accepts the existence of an additional back rounded vowel /ʊ/ as claimed by Olson (2022), that [wo] and [wu] have emerged from the transphonologisation of a now lost preceding back vowel, or some other origin of /w/, the contrast of forms such as *kwu* ‘jump’ and *ku* ‘drip’ can be straightforwardly explained by the presence of an additional |U| element in forms presenting optional surface /w/.<fnref n="40" /> So long as |U| is associated to an onset position, both [kwu] ~ [ku] ← /kwu/ and [ku] ← /ku/ can be analysed as containing the same underlying vowel /u/. Idem for the mid vowel /o/ with the addition of |A| (see [3]). In keeping with the authors’ position that rounded and unrounded pairs share a single representation, positing a floating |U| as an integral part of the phonological representation of words which always surface with the rounded vowel perfectly predicts forms where surface [u] and [o] are systematically preserved.

Synchronically, so long as /w/ |U| can be expressed as [w], /kʷo/ ‘walk’ → [kʷo] (2e), the underlying phonological pattern can be abstracted. However, the fact that |U| can be absorbed into a following back vowel in the output, /kʷo/ → [kɔ], creates opacity and the

<footnote>metathesis or some complex coarticulation between the bilabial glide and /k/. Idem for ‘walk’ Alt. *kʷo* vs Boy. *wкв* (2e) and ‘stop’ Alt. *kʷɔ* vs. Boy *kwкв* (2f).</footnote>

<footnote n="40">⁴⁰ Althabégoïty (2024), §3.2) has in fact discussed various possibilities worthy of future exploration from a comparative perspective, including the existence of contrastive “velar” consonants.</footnote>
conditions for reanalysis, i.e. the impression that [u] and [w] are primary phonemic con-
trasts after /k, g, ɣ/. The reassociation of underlying |U| from the attested [w] into the
following vocalic nucleus would provide the conditioning for the emergence of two new
phonemes: /u/ and /o/ on the one hand who have maintained their round character through
the absorption of preceding |U|, and /w/ and /ɣ/ on the other, through delabialization be-
fore plain velars. Returning to the central notion of *contrast activation*, this limited dis-
tribution of /o/ and /u/ must be understood as a consequence of the historical phonology.

Althabégoïty, Galla. 2024. Étude des verbes en ngbugu Langue du groupe banda (oubanguien, Niger-Congo) de Centrafrique. Université d'Orléans, PhD Thesis. https://theses.hal.science/tel-05023143. Backley, Phillip. 2011. An Introduction to Element Theory. Edinburgh: Edinburgh University Press. Boyeldieu, Pascal. 1989. Lexique ngubugu, unpublished manuscript, accessed via ReFlex (01/03/2025). Boyeldieu, Pascal & France Cloarec-Heiss. 2021. Les choix vocaliques de deux parlers banda: correspondances ou ressemblances régulières ? In Leçons d'Afrique. Filia-tions, ruptures et reconstitution de langues. Un hommage à Gabriel Manessy. (Ed.) R. Nicolaï, Peeters, 181-200. Campbell, Lyle. 2020. Historical linguistics: an introduction. Fourth edition. Cambridge, Massachusetts: The MIT Press. Éboué, Félix. 1918. Langues Sango, Banda, Baya, Mandjia: notes grammaticales, mots groupés d'après le sens, phrases usuelles, vocabulaire. Par-ris: E. Larose. Harris, John. 2005. Vowel Reduction as Information Loss. In Philip Carr, Jacques Durand & Colin J. Ewen (eds.), Current Issues in Linguistic Theory, vol. 259, 119–132. Amsterdam: John Benjamins Publishing Company. Hoenigswald, Henry M. 1960. Language Change and Linguistic Reconstruction. Chicago: University of Chicago Press. Olson, Kenneth. 2022. On the Ngbugu vowel system. In Descriptive and theoretical approaches to African linguistics, 9–23. Berlin: Language Science Press. Nougayrol, Pierre. 1997. Lexique gbaga nord. (Ed.) Guil-laume Segerer & Sébastien Flavier. RefLex. Segerer, Guillaume & Sébastien Flavier. 2011–2023. ReFlex, Reference Lexicon of Africa. Paris, Lyon. https://reflex.cnrs.fr/. Theret-Kieschke, Régine. 1998. Esquisse phonologique du ngbugu. Bangui: SIL International. Touguele, Samuel. 2008. Phonologie et morphologie de la langue ngbugu. Yaoundé: Université de Yaoundé Master’s Thesis.
ARGUMENTS AGAINST: A LATENT PHONEMIC SPLIT – DISCUSSION WITH FABIAN ZUK

The reviewer's account, rather than supporting the idea of a rounding contrast activation between back vowels, argues for a contrast originating within the onset itself (labialized vs. non-labialized onsets), motivated by an ongoing secondary split. The rounding contrast, being apparent, would thus be only a side effect of the interaction between vowels and the segmental material of the onset.

THE USE OF COMPARATIVE DATA

The reviewer begins his demonstration by comparing data from Ngbugu and related languages, aiming to justify that the existence of unrounded back vowels is a recent innovation. Yet, his choice to compare Ngbugu data with Banda-Banda data from Eboué (1918) does not seem appropriate to us. The reviewer presents the Banda-Banda data as representative of an earlier stage of the Ngbugu language, or even as a kind of proto-Banda, which is not the case. He relies on Banda-Banda data to argue that [w] and [χ] are recent realizations of rounded back vowels. However, according to various authors, Banda-Banda and Ngbugu belong to distinct language groups within the Banda family: Ngbugu is classified as South Central (Cloarec-Heiss, 2000: 193) or Southwest Bandaic (Glottolog), whereas Banda-Banda is Core Central Bandaic (Glottolog). Northern Gbaga, the other language the reviewer compares, belongs to the North Central group (Cloarec-Heiss, 2000: 193). Like the reviewer, we believe that comparison among Banda languages can be fruitful for understanding diachronic processes, but such comparison should involve a larger number of languages to be more informative.

No proto-Banda has been reconstructed, and such reconstruction may not even be possible given the history of this language family. Within the Banda family, similarities be-
tween languages are more significant in the lexical than in the morphological or phono-
logical domains (Cloarec-Heiss, 2000). Cloarec-Heiss (1995: 2000) and Boyeldieu &
Cloarec-Heiss (2001) suggest that Banda languages probably emerged from the massive
adoption of an Ubangian lexicon by speakers of Sara-Bongo-Bagirmi languages (Central
Sudanic, non-Ubangian, non-Niger-Congo). According to Boyeldieu and Cloarec-Heiss,
who compared Ngbugu and Banda-Linda, the current languages result from a “process of
massive relexification followed by one or both languages from a third source”
(2001: 204).

Contrary to the reviewer's suggestion, we do not think that comparison of Ngbugu
with other Banda languages indicates a recent appearance of [u] or [ʊ]. The available
data for 42 Banda varieties in the RefLex database show that contrasts among back vow-
els are widespread. An o/ɔ opposition is present in most Banda varieties, corresponding
to the o/χ opposition in our Ngbugu data. The u/u opposition is also attested in several
Banda varieties. Although current observations do not allow us to propose a clear dia-
chronic scenario explaining the presence of this opposition, we provide some comparative
evidence below. This topic has been partially treated in Althabégoïty (2024), from which
we reproduce and translate the following passage:

According to available transcriptions, the u/u opposition is productive in velar context
in Langbasi (Cloarec-Heiss 1997 on RefLex), Northern Gbaga (Nougayrol 1997 on Re-
fLex), Mbanja (Tingbo 1971 on RefLex and Boyd p.c.) and Dakpa (Segerer 1996 on Re-
fLex). According to these same transcriptions, these two phonemes correspond to a single
phoneme /u/ in other varieties (see Linda (Moñino 1988 and Cloarec-Heiss 1996 on Re-
fLex) for example).
(1) w/u OPPOSITION IN NGBUGU, LANGBASI, NORTHERN GBAGA AND MBANJA

<table><thead><tr><th></th><th></th><th>Ngbugu<br>(Alt.)</th><th>Ngbugu<br>(Boy.)</th><th>Lang.</th><th>Nor. Gbaga</th><th>Mbanj.</th><th>Dakpa</th><th>Lin.</th></tr></thead><tbody><tr><td rowspan="2">/w/</td><td>'thigh'</td><td>[kū]</td><td>kū</td><td>ākū</td><td>ōkū</td><td>kūkū</td><td>ākū ~ ōkū</td><td>ākū</td></tr><tr><td>'bug'</td><td>[kú]</td><td>kú</td><td></td><td>kùkú ~ òkú</td><td></td><td>ákú</td><td>ōkū</td></tr><tr><td rowspan="2">/u/</td><td>'wound'</td><td>[kwù~ kù]</td><td>kwù</td><td>kùkù</td><td>ùkù ~ òkù</td><td>kùkù</td><td>àkù</td><td>àkù</td></tr><tr><td>'trap'</td><td>[kwú~kú]</td><td>kwú</td><td></td><td>Ókú</td><td>kúkú</td><td>ákú</td><td>ōkū</td></tr></tbody></table>

(Althabégoïty 2024: 69-70)

The u/w opposition is also attested in non-velar contexts in Mbanja (dwī~dwīdwī'spear' contrasts with dūdū 'mortar'). In Dakpa, forms with /w/ appear to alternate freely with /u/ and/or /i/ (see table 2). We can then observe correspondences with vowels /i/ and /u/ in other varieties.

(2) TABLE 2 - /w/ IN NON-VELAR CONTEXTS IN MBANJA AND DAKPA

<table><thead><tr><th></th><th></th><th>Ngbugu<br>(Alt.)</th><th>Ngbugu<br>(Boy.)</th><th>Lang-<br>basi</th><th>North<br>Gbaga</th><th>Mbandja</th><th>Dakpa</th><th>Linda</th></tr></thead><tbody><tr><td>/u/<br>/w/<br>/(i/)</td><td>'spear'</td><td>[dū]</td><td>dī</td><td>dūdū</td><td>ūdū</td><td>dū~dūdū</td><td>ādū~ādū</td><td>ōdū</td></tr><tr><td>/u/<br>/w/<br>/i/</td><td>'to<br>seek'</td><td>[pu]</td><td>pu</td><td>pì</td><td>pu</td><td>pù</td><td>pù<br>pū~pū~pī</td><td>pì</td></tr><tr><td>/u/<br>/w/</td><td>'to<br>break<br>down'</td><td>[?u~?wu]</td><td>?wu</td><td></td><td></td><td>?w</td><td>?u</td><td></td></tr><tr><td>/i/<br>/u/</td><td>'to give<br>birth'</td><td>[zì]</td><td></td><td>zu</td><td>zu</td><td></td><td>zī~zì</td><td>zū</td></tr></tbody></table>

In other Banda varieties, the u/w opposition is not attested in velar contexts but occurs elsewhere. In Langba (Boyd & Boyeldieu 1997, RefLex), for instance, dw 'count' contrasts with dū 'spear', and sw 'sew' with su 'harvest'. Similar contrasts are attested in
Ngbundu (Cloarec-Heiss & Boucquiaux 1997, RefLex), where dw ‘count’ contrasts with dū ‘spear’.

Given the frequent attestation of the o/y opposition in most Banda languages and the
presence of u/uy contrasts in six Banda varieties, we do not think that comparative data
support the view that these oppositions are recent innovations.

SYNCHRONIC ORIGIN OF THE CONTRAST

The core aspect of the reviewer's hypothesis — that the relevant contrast results from the coexistence of labialized onsets (Cw, Cʷw) and non-labialized ones (C, Cʷ) — corresponds to that of Boyeldieu and Cloarec-Heiss (2001) (for a discussion of other possible analyses, such as two series of velar consonants, diphthongs, syllabic format oppositions, or rounding distinctions between two series of back vowels, see Althabégoïty 2024: 64–69). However, this account complexifies the inventory of consonantal onsets in the language: if we adopt it, we must add the Cw and Cʷw types to the already existing C and Cʷ types.

Moreover, this analysis does not explain the distribution of the hypothetical /w/ phoneme — or, rather, that of the underlying |U| element, which may emerge as [w] in case it links to an onset position, or as a rounded vowel [o]/[u] in case it is associated to a nucleus<fnref n="41" /> — on synchronic grounds, thus ignoring the question as to why the relevant contrast is (mostly) exclusive to velar contexts.

To legitimate his move, the reviewer rather seems to rely on a diachronic argument: Comparing Ngbugu with Northern Gbaga, he suggests that some Ngbugu /w/ may correspond to the presence of an additional rounded vowel in the latter. We find this interpretation unlikely, as such additional vowels are also found in probable cognates to Ngbugu forms that do not have [w] (e.g. ‘thigh’ [kwī] in Ngbugu, ōkuī in Northern Gbaga).

<footnote n="41">⁴¹ This is our own interpretation of the following passage: ‘|U| [i.e., the underlying couterpart of the [w] segment] can be absorbed into a following back vowel in the output, /kwo/ → [wo].’</footnote>
While we acknowledge that the reviewer’s account is insightful — particularly for its success in explaining the distribution of unrounded and rounded vowels in velar/dorsal environments, as well as the potential presence of the [w] segment in Cw sequences — we therefore claim that the restrictions laying on the presence/absence of contrast is more successfully captured through our approach.

As a final word, while in diachrony both concepts of neutralization and secondary split are attested, only the concept of neutralization has so far been applied synchronically to our knowledge. The concept of activation that we propose could therefore be seen as the synchronic counterpart of a secondary split. For this reason, we believe that the data we present constitute a system that can be described synchronically.

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