Understanding the distribution of lexical tones is an important aspect in the description and analysis of tone systems. Most researchers agree that Boro is a tone language (Weidert 1987) and that Boro uses lexical High and Low tones and sometimes a default Mid tone is also assumed (Sarmah 2004). These tones can be employed to distinguish lexical meaning of Boro words as in (1) below (Sarmah 2004):

The tone bearing unit (TBU) in Boro is the syllable and the rightmost TBU hosts the lexical tone in disyllabic words. Joseph and Burling (2001) reiterate the view expressed in Burling (1959) and come to the conclusion that Boro has a two-tone system. In addition to this, Joseph and Burling (2001) also mention the presence of the phenomenon of tone spreading in Boro towards the right. Joseph and Burling (2006), while presenting a description of the comparative phonology of the Boro-Garo languages, reiterate Joseph and Burling (2001) by describing a two-tone system for Boro. They found no evidence for the four tones claimed by Bhattacharya (1977). Bhattacharya (1977) focused mainly on the tone pattern in monosyllabic words, but other studies have shown that Boro disyllabic words can have only one of the two tone patterns, whether it be a High tone or a Low (Joseph & Burling 2006). Sarmah (2004) presents further evidence to show that Boro has two tones: High and Low. Extensive discussion of Boro tones can be found in Das & Mahanta (2018), and Das (2017).

In our discussion in the following sections we do not claim that Boro is a densely tone marked system. It could be close to what Voorhoeve (1973) describes as a ‘restricted tone system’. Notably we do not make any proposition regarding its adherence to a pitch-accent system as there are no clear properties that a pitch-accent language attests. Hyman (2009: 213) notes “… alleged pitch-accent” systems freely pick-and-choose properties from the tone and stress prototypes, producing mixed, ambiguous, and sometimes analytically indeterminate systems which appear to be “intermediate”. Hyman presents a rigorous discussion arguing for the absence of any pitch-accent prototype, nor can prosodic systems be treated as a continuum placed along a single linear dimension. As far as Boro is concerned, apart from Hyman’s arguments, the attributes of stress are also not entirely clear and therefore Boro is not amenable to an analysis as a pitch-accent language where lexical tone is delimited to the vicinity of the stressed syllable.

In the following section, we attempt to look at a few delimiting properties of intonation across these types of languages in order to see if there’s indeed a pattern for such restricted tone languages. It appears that there are indeed intonational properties common to languages which attest lexically distinctive f0, whether restricted or not, and they may allow more intonational properties to appear but there are no fixed ways in which they can be predicted to show their intonational and prosodic effects, making it more difficult to classify these languages.

Section 1 describes the distribution of tones in Boro. Section 2 deals with the domain of prosodic word as the domain of tone assignment in Boro. Section 3 describes the methodology adopted for the experiments presented in the chapter and the speech material designed for the experiments. Section 4 highlights the way lexical tones surface at the sentence initial, medial and final positions. It also describes the basic intonation patterns in Boro and shows how downstepping and declination influence lexical tones. This section also shows how left edge boundary tone influences initial lexical tones in IPs. Section 5 presents a phonological account of intonation in Boro, based on the nature of prosodic phrasing allowed in this tone language. This section also highlights the fact that the left edge of Boro IPs are marked by an LH% boundary tone which interacts differently with the initial L and H lexical tones. Section 6 discusses the attributes of the Intonational Phrase in Boro. Section 7 summarizes the findings presented in this paper.

The question whether tone languages and ‘pitch accent’ languages vary in terms of intonation does not lead to any forthrightly viable answers. This is because both tone languages, and the languages commonly identified in the literature as pitch accent languages, not only attest intonational properties which are seen in intonation only languages, but also show deviations which are not particular to any of these groups.

Just like tone languages, pitch accent languages like Swedish and Norwegian, have simpler intonation systems than, for instance, English, a language without lexical tone (Gussenhoven & Vliet 1999). The segmental site for tone-intonation interaction in Venlo Dutch, a language variety that distinguishes two lexically distinctive tonal accents, is the IP final syllable where the boundary low tone (L%) spreads leftward to a free TBU (mora) to generate two L targets at the right edge (Gussenhoven & Vliet 1999). Similar to these languages, certain Oto-pamean languages of Mexico, like Shekgalagari, restrict their lexical tone contrast to pre-final syllables reserving word-final syllables for intonational contrasts (Hyman & Monaka 2011). In Shekgalagari, the L% lodges itself on the penultimate syllable where penultimate lengthening lends a second mora for L% association. The lexical high tone in Kikuyu undergoes flattening when it is followed by L% (Clements & Ford 1981). In Mayen Franconian, the final L of the HL% question tone is truncated when it is preceded by an L* and a H tone in the same syllable (Gussenhoven 2000).

Prosodic boundaries may be inserted before or in the vicinity of the focused constituent (Hartmann 2008). This is true for both ‘pitch-accent’ and typical tone languages. The relationship between focus and phonological phrasing is well known in Japanese (Poser 1984), Hausa (Inkelas 1998), Korean (Chao 1990), Modern Greek (Condoravdi 1990), and Shanghai Chinese (Selkirk & Shen 1990). Kanerva (1990) describes how narrow focus within the verb phrase in Chichewa results in an increase in the number of p-phrases. When only the verb is placed under narrow focus, a phonological boundary forms after the verb in the verb phrase. The entire verb phrase forms one p-phrase when the whole VP is focused. Downing (2006) describes the focus marking strategy in Chitumbuka (Chitumbuka has restricted tone, like Boro) and highlights how prosodic phrasing marked by lengthening of the penultimate syllable of the focused constituent marks a constituent prominent. Downing (2008) demonstrates how in Chichewa, Chitumbuka and Durban Zulu, phonological rephrasing functions as the prosodic correlates of focus. Thus, analyzing the tonal system of a language without taking into account the intonational structure may result in incomplete understanding of the data (Gussenhoven 2012). The integration of lexical and intonational tones played an important role in the description of Japanese in the work by Pierrehumbert and Beckman (1986), and later in that of Norwegian, varieties of Basque and Dutch dialects (Gussenhoven 2002).

Another aspect where there’s a lot of overlap among languages pertains to boundary tones. Boundary tones (Pierrehumbert 1980) are distinguished from other tones by their distribution. These tones generally appear on the edgemost syllable of a domain, such as the last syllable of an IP. They differ from lexical tones in having a phrasal distribution and their functional presence may be seen as a means to distinguish sentence types (Myers 2004). Boundary tones often have a strong effect on the f0 scaling of other tones in the utterance. In Chichewa, the f0 values of lexical high tones are markedly higher in questions than in statements (Myers 1996). f0 peaks are higher in questions than in statements in languages as diverse as Mandarin (Ho 1977; Shih 1987), Russian (Svetozarova 1975), Swedish (Gårding 1979), Vietnamese (Nguyen and Boulakia, 1999), Kikuyu (Clements 1981), Jita (Downing 1995) and Hausa (Inkelas & Leben 1991). Another important point has emerged in the discussion of boundary tones in tone languages as well as in pitch-accent languages, that is, boundary tones can sometimes migrate away from the originating boundary, as shown by Hyman (1990) for Luganda super-high tones, and by Gussenhoven (2000) for Dutch. The LHLH string marking accentual phrase is Seoul Korean is reduced to just an initial LH if the accentual phrase consists of three syllables (Jun 1993; 1998). Accentual phrases in Northern Bizkaian Basque are characterized by an initial pitch rise due to a sequence of LH tones where the target of L occurs on the first syllable and the H aligns to the second syllable (Gussenhoven 2004). In Northern Bizkaian Basque the realization of the LH initial boundary sequence depends on the availability of syllables. Neither of the initial L or H boundary tones surface when the first syllable is occupied by H*. In instances of H* surfacing on the second syllable, only the L boundary tone of the LH sequence is realized (Gussenhoven 2004).

Boro shows a mix of the properties outlined above. While tones are not deleted to allow for more intonational tones (except the final H) to appear, there are indeed other intonational characteristics of note. They include a left edge boundary tone of LH% which is especially pronounced if there’s a lexically specified low tone at the left edge (showing some similarity with Basque but not entirely), deletion of a final H tone, and tonal scaling of H tones vis-à-vis the presence of other H and L tones. Downstepping is also widely attested and these downstepped tones serve as cues to prosodic boundaries in the nature of their distribution. More research on intonation in tone languages, restricted or otherwise, will help us to understand if certain types of tone languages exhibit these intonational properties. Till then it is safe to say that Boro intonation shows adaptive behavior and restricts deletion of underlying tones but does create additional tonal targets.

Boro suffixes without tonal specification do not form their own PrWd. Rather they get attached to the PrWd of the stem.

In such a situation they surface with the lexical tone of the stem. The pitch contours presented in Figure 1 for the Present Habitual (abbreviated as PRSNT HAB) forms of verbs provide acoustic evidence for this. It is seen that in /tʰáŋ-ɯ/ ‘go-PRSNT-HAB’ the high tone on the suffix has shifted from the stem and in /lɯ̀ŋ-ɯ/ ‘drink-PRSNT-HAB’ the low tone has shifted to the suffix from the verb stem. Disyllabic stems followed by toneless suffixes present a slightly different picture. Instances of tone distribution within a disyllabic stem + suffix domain shows that the PrWd domain in Boro is mostly disyllabic. It is observed that the f₀ signal for the tone does not shift from the stem to the suffix, when a toneless suffix is added to a disyllabic stem, but it spreads. Figure 2 provides an instance of this.

Tone spreading to the third syllable is also noticed when the case marking suffix /-ao/ and the negative marking suffix /-akʰɯi/ are added to disyllabic stems. Figure 3 present the pitch contours of /ɡozoù-ao/ ‘high-LOC’ and /hatʰaí-ao/ ‘house-LOC’ where the locative case marker /-ao/ occurs as the third syllable.

Evidence from such disyllabic stems plus toneless suffixes in this investigation has revealed that the locus of tone alignment or where it will spread or shift will depend crucially on the number of syllables. This phenomena does not prominently surface in the case of low tone stems due to the low f₀ range of low tone and toneless syllables. But high tone spreading to a toneless suffix, following a disyllabic stem, has been observed for several stems and suffixes examined in this investigation. A list of such stems and their suffixed forms are presented in Table 2 below.

In the autosegmental literature, tone phenomena of spreading and shifting could be understood as locally bounded and their representation showed how shifting requires spreading followed by deletion of the tone in the original TBU (Kenstowicz & Kisseberth 1990). The spreading and shifting of Boro tones is represented in Figure 4.

The correspondence between syllable length and prosodic word domain has been discussed in relation to other languages too. Zec (2002) observes that the prosodic word status in Serbian is diagnosed by pitch accent prominence, and disyllabic function words are matched with prosodic words, but those corresponding to a single syllable are not. Lehiste (2004) argues that in Serbo-Croatian, Swedish and Estonian, contrastive tones require a disyllabic domain to manifest. Examination of disyllabic stem plus toneless suffixes in Boro also suggests that the disyllabic stems, whether derived or non-derived, form a PrWd domain and the lexical tone is associated to the right edge of this domain.

Tone alignment in Boro in the context of word formation processes reveals the affixes which have their own tonal specifications. Some suffixes are found to have their lexical tones, but their addition does not alter the tonal nature of the stems. Inkelas & Zoll (2007), from Poser (1984) described that the dominant or recessive suffixes could be either high tones or low tones. Suffixes in Boro, irrespective of their lexical tonal status, belong to the recessive category. Prefixes belong exclusively to the dominant class as their addition changes the tonal specification of the stem. Although prefixes and suffixes in Boro are divergent in the way lexical tones are specified, neither of these always surface with their tonal specification. When suffixes become part of the disyllabic PrWd domain, they surface with the lexical specification of the stem. In such a situation they can surface with their lexical specifications. The examples below in Table 3 demonstrate this alignment in Boro.

Underlyingly non-tone bearing suffixes surface with the tone of the stems. When toneless suffixes form part of the PrWd, the lexical tone of the stem shifts to the right edge. Many languages define the domain of prosodic words according to their phonological properties. Although the lexical tones of both stems and suffixes can influence the principle of PrWd formation, these tones undergo further modification when they surface at the phrasal level.

The study presented in this paper is based on data collected from 4 male speakers of Boro. The data set consisted of 140 scripted sentences which included neutral statements and statements expressing narrow focus by the process of ex-situ focus marking allowed in Boro. The sentences differed from each other in the sequence of lexical tones as well as in length. Each of the participants produced 7 renditions of all the sentences with sufficient amounts of pause in between. The first and the last iterations were not taken into account. In this way a total number of 2800 (140 sentence × 4 speakers × 5 recordings) recorded sentences constituted the data series for this experiment. The meaning of each of the sentences was repeated after each rendition of the sentences to remind the speakers of the kind of meaning they are supposed to produce.

The first set of data examines whether the phenomenon of downdrift/declination influences the pitch contours of utterances with a sequence of similar tones. A number of sentences in this set of data consisted of sequences of only high tones or low tones. A sequence of either three lexical tones or four lexical tones feature in these sentences. Within this group, 6 sentences consisted of only three lexical tones (3 each for low and high tones) aligned to the right edges of PrWds. The other 8 sentences within this group consisted of four lexical tones (4 each for low and hign tones) aligned to the right edges of PrWds. This experiment was crucial to understand downstep and downdrift patterns in Boro.

The second set of data examines tone contrast in sentence initial, medial and final positions. The corpus for this data set included 40 sentences consisting of 20 pairs of related (near homophonous) constructions. These pairs of sentences differed from each other in only a high tone word occurring in place of a low tone word or vice versa. This is shown in (2). The substituted words with contrastive tones consisted of equal number of syllables and the rest of the text was also kept constant. In (2a) /daodɯí/ ‘egg’ is substituted by /bedòr/ ‘meat’ with the rest of the sentence remaining the same. In the other two examples, in (2b) /zá-kʰor/4 ‘gluttonous’ is substituted by /lɯ̀ŋ-kʰor/ ‘drukard’ (sentence medial position) and in (2c) /tʰáŋ-ɡɯn/ ‘go-FUT’ is replaced by /pʰɯì-ɡɯn/ ‘come-FUT’ (sentence final position). For each example, a phonetic notation is given followed by a morphological gloss and a translation.

The primary objective of this experiment was to examine whether the pitch contours of words change depending on their occurrence in phrase initial and medial positions. This experiment provided us with sufficient understanding of boundary patterns in Boro in different positions and repeated sentence patterns helped us to locate boundary tones in Boro. The final occurrence of the words were not examined since Boro follows Subject + Object + Verb word order and the final sentential slot is often occupied by the verb along with its inflections.

Only alternative questions5 in Boro provide the context of the final occurrence of a non-verbal element. Thus the pitch contour of the initial occurrences of the words /daodɯí/ ‘egg’ in (3a) and /bedòr/ ‘meat’ in (3b) was compared with the medial and final occurrence of them in (3c) and (3d).

The third data set consisted of a series of 40 sentences with the same lexical items or sequence of lexical items occurring in sentence initial and medial positions. The objective of evaluating the pitch contours of such sentences was to examine how the same sequence of lexical tones in Boro surface depending on their sentential contexts. In the sentences in (4), the sequence of LH tones in Boro as seen in the word /ɡizì zí/ ‘torn cloth’, occur sentence initially and medially. Other combinations of lexical tones which belong to such pairs of sentences are HL (e.g. /nɯ́ŋ-nao zɯ̀o/ ‘my rice beer’), LL (e.g. /àŋ-nao zɯ̀o/ ‘my rice beer’) and HH (e.g. /nɯ́ŋ-nao bɔ́n/ ‘your firewood’).

The fourth set of data included sentences with embedded clauses and longer phrases in subject or object positions. Constituents of such varying lengths were used to investigate the nature of phrasing allowed in Boro. This set of data consisted of 26 sentences. The last set of sentences in the data series are instances of sentence internal constituents preposed to sentence initial position. Boro allows this kind of construction for ex-situ focus marking. The sentences in (5) present some instances of this.

The experiments deliberately avoided conversational speech for a number of reasons. One primary reason was the near-impossibility of eliciting the exact test items type in spontaneous speech. The latter reason becomes clear when one takes into account the fact that sentences consisting of words with both lexical high and low tones cannot be built into the same conversation as these lexical items would mean different things. Conversational speech also needs to allow the participants enough time to produce the required intonational type which would rob the experiment of its naturalness. This experiment did not opt for this elicitation method owing to these practical yet unavoidable problems.

Four participants (male) participated as the subjects for this investigation. Each subject rehearsed the randomized list of scripted sentences in the presence of the experimenter. After the subject was familiarized with the sentences, she read them individually into a unidirectional headworn microphone connected with Edirol Roland R-09HR via xlr jack. The recordings were digitized at a sampling frequency of 44.1 kHz and 32 bit resolution. The subjects were allowed to re-record a sentence if they had apprehensions about the words or the intended meaning. The speakers produced the words embedded in the sentence frame. The speakers were between 22–28 years of age and they were born and raised in their native villages where the recording was conducted. All of them were from comparable socio-economic backgrounds. The experiment was carried out in a quiet environment at Bhatipara, Kazigaon and Bashbari villages. All the speakers were college educated and they had elementary knowledge of Assamese. None of the speakers had any previous record of hearing or listening impairment. Each speaker was paid a small fee for their participation in the production experiment. According to Basumatary (2005), the western Boro variety spoken in the districts of Kokrajhar, Dhubri and Chirang is recognized as the standard form of Boro language. From this viewpoint, the data collected for the present experiment can be described as the standard variety of Boro.

Each speaker produced 6 iterations of each word in the data set embedded in the sentence pattern mentioned above with sufficient pause in between. The subjects were asked to read aloud the sentences written in the Devnagari script. A unidirectional head-worn microphone connected with Edirol Roland R-09HR via xlr jack was used for the recordings. The recordings were digitized at a sampling frequency of 44.1 kHz and 32 bit resolution.

Each iteration of the individual words were first extracted and saved as separate wave files using the speech analysis software- Praat 5.3.04_win32 (Boersma and Weenink 2012). Individual sound files of the words were further segmented into the phoneme level and Praat TextGrid files were created for each word. Segmentation was based on spectrograms, zoomed waveforms, in addition to the aural verification of sound files. The segmented files were processed with a Praat Script [ProsodyPro] (Xu 2013) for obtaining measurements of f0. This script provides various measurements of individual wave files such as time-normalized f0 where the f0 in each interval is divided into the same number of points (default = 10), and thus the points 1–10 belong to the first interval and the points 11–20 to the second interval and so on. The script also provides values for meanf0, maxf0, minf0, duration and so on. The averaged normalized f0 values of all the iterations of each word (5 speaker × 5 iterations = 25) were plotted as line graph in order to observe the difference between the pitch contours of the words before and after affixation. Statistical tests were done in SPSS for evaluating whether the nature of difference in f₀ is statistically significant or not.

Most of the experimental blocks discussed above are not possible to be compared with one another as they constitute different sentential patterns. The data set are also controlled for their individual segments, tones and syntactic organization. These general questions are approached in this paper: 1) What role does local and global f 0, and to a certain extent, intensity and duration play in the intonational organization of Boro? 2) How are tones affected in this intonational organization? 3) Do tones signal intonational organization in any way? 4) Are there intonation specific tones in Boro?

An important aspect of the way tones surface in tone languages is the way context influences their f₀ trend. This section describes the surface realizations of tones in Boro in IP initial, medial and final contexts. The results described here are from the second experiment described in the section on materials.

Tones produced in isolation can display pitch trends different from the way they are actually realized while occurring in the contexts of other tones. Figure 6 presents the time normalized pitch contours aggregated for 20 tokens (4 speakers × 5 repetitions) for a homophonous and an ambiguous sentence. The only difference between the two sentences is the tone of the verb /baí/ ‘break’ as opposed to that of /baì/ ‘buy’. In both the sentences the verbs are inflected with a verbal suffix /–nai/ and a nominal case marker /–á/. Generally, High tones in Boro surface with a rising contour and low tones with a falling contour or a low level contour. It can be seen in Figure 6 that /baí/ ‘break’ surfaces with a rising contour and the pitch continues to rise till the nominative marker /–á/. However, the pitch contour of the inflected form of /baì/ ‘buy’ shows a falling contour up to the verbal suffix /–nai/ which surfaces with the lexical tones of the stems in both the sentences.6 Thus the nominative suffix /–á/ preserves its lexical specification even when it is preceded by a low tone aligned to /–nai/ in /baìnaiá/ ‘buy-Verb-nom’. The contrast between the pitch contours for /baí-nai-á/ ‘breaking’ as opposed to that of /baì-nai-á/ ‘buying’ shows that lexical tones in Boro preserve their lexical f₀ trend while occurring sentence medially. Contextual influence on lexical tone has been described in studies on Mandarin Chinese (Xu 1997), Thai (Potisuk et al. 1997) Yoruba (Laniran & Clements 2003) and Cantonese (Wong 2016).

The left panel of Figure 7 shows that the pitch rise for the lexical H tone on the second syllable of /daodɯí/ ‘egg’, is scaled lower when it is in the IP final position. The pitch contour surfaces with a comparatively retracted peak compared to the scaling of the f₀ peak for the other two occurrences of the word. The right panel of Figure 7 is quite important to understand the variances observed with respect to lexical low tone in IP initial position. The initial occurrence of /bedòr/ ‘meat’ is compared with its respective medial and final occurrences (as far as the shape of the pitch contour is concerned). The medial and final occurrences of /bedòr/ ‘meat’ surface with a falling pitch contour which is a characteristic pattern of Boro low tones in their citation forms. The initial occurrence of the word results in a raised pitch contour on the second syllable of /bedòr/ ‘meat’. The mean f₀ of the vowel of first syllable (158.49 Hz, n = 20) is lower than that of the second syllable (171.22 Hz, n = 20) of the phrase initial occurrence of /bedòr/ ‘meat’. This shows that the IP initial low tone surfaces with a low rise contour. Section 4.2 relates the scaling difference between the two syllables of the IP initial occurrence of /bedòr/ ‘meat’ to an intonational left edge boundary tone. Acoustic evidence presented in this section reveals the following intonational aspects of pitch contours of Boro sentences: (a) Tones preserve their lexical specifications only when they occur medially in IPs and (b) IP initial L tones surface with a rising f₀ trend.

Boro IPs show that the language attests both processes of downstepping and declination of f₀ targets mentioned above. In sentences consisting of a sequence of high tones, each of the non-initial high targets is realized 30–40 Hz lower than the previous one. The pitch contour presented in Figure 7 provides evidence for two interesting prosodic facts of Boro. The first one is that the second high tone (H2) surfaces lower than the first one (H1). Mean f₀ of H1 (181.85 Hz) is higher than that of H2 (167.67 Hz). The third H tone (H3) surfaces lower (146.83 Hz) than that of H2. No low tone intervenes between the sequence of H tones in Figure 8 because in Boro polysyllabic words the lexical tones do not align to the first syllable. The rising pitch contours for all the three non-final high tones are quite obvious in Figure 8. Although both the ultimate and penultimate syllables in /daodɯí-á/ ‘egg-nom’ surface with high tone, the second high tone surfaces higher than the first one. This shows that downstepping in Boro cannot affect tonal scaling within the PrWd domain.

Pitch tracks of sentences with an initial LH sequence are compared (in Figure 9 below) to that of initial HH sequences (the second tone bearing lexical unit remains constant). Figure 9 compares the time normalized pitch contours of two sentences where (1) /tʰaizoú/ ‘mango’ occurs as the second constituent and it is preceded by /nɯ́ŋ-nao/ ‘you-POSS’ and (2) /tʰaizoú/ ‘mango’ occurs as the second constituent and it is preceded by /àŋ-nao/ ‘I-POSS’ in the other. The averaged f₀ maximum (Maxf₀) (n = 20) of the second syllable of /tʰaizoú/ ‘mango’ is higher (163.21 Hz) when it is preceded by /nɯ́ŋ-nao/ ‘you-POSS’ as compared to the one following àŋ-nao ‘I-POSS’ (155.42 Hz). Two more Boro intonational facts can be inferred from Figure 9. In a sentence with an initial LHHL sequence of lexical tones, the first peak aligns to the first H tone which is followed by a downstepped H, before the pitch falls to the low boundary tone. Secondly the pitch register of the whole IP is lowered since it begins with an L tone. To understand this, the pitch contour for the HHHL sentence in the left panel of Figure 8 can be compared with that of the LHHL sentence in the same Figure.

Boro H tones are scaled lower when they follow another high tone or a low tone. This is influenced by the post-lexical domain where downstepping is commonly attested at the ip level in Boro. All our evidence shows that terraced-tone type downstepping is an attribute of the intermediate phrase. This precise environment is a sequence of H tones in the ip domain and this downstepping never trespasses the ip boundary. It is possible to analyze this as a floating L tone in the ip domain but it’s not clear what that postulation would mean for the phonology of Boro in general. Hence, we will rest our case in favour of an ip level downstepping domain in Boro.

The phenomenon of raising of L tone under the influence of H tones in the vicinity has been already attested in Thai (Pontisak et al. 1994) and Yoruba (Laniran & Clements 2003). In Akan, the medial L tone is raised by 10 Hz whereas the initial L in an LHLH sequence is not subject to any raising. (Genzel 2013). Visual examination of pitch tracks of Boro sentences with HL sequences has revealed that Boro L tones are raised when they are preceded by H tones. Figure 10 presents averaged time normalized pitch contours of two sentences differing in the tonal specification of the first element. The Mean f₀ of the second syllable of /bedòr/ ‘meat’ aggregated for all the speakers (n = 20) is found to be more (157.15 Hz) when the word is preceded by /nɯ́ŋ-nao/ ‘you-LOC’. This can be compared to the aggregated Mean f₀ of the second syllable of /bedòr/ ‘meat’ (n = 20) (150.46) when the word is preceded by àŋ-nao ‘I-LOC’. These results show that low tones in Boro are influenced by high tones and undergo raising when they are preceded by H tones. The pitch contours presented in Figure 10 also show how a sequence of LLHL sentence surface at the IP level in Boro. It can be seen that a late high tone in Boro may surface with a lower pitch than an early L. The late H in the LLHL sentence pattern is downstepped following the pattern of phonetic lowering discussed in section 4.2.

It has been already shown in Figure 8 that all-H tone sentences in Boro result in downstepping of non-initial H tones. The all-L sentences in Boro do not show similar amount of pitch drop in the non-initial tones as is the case found to be in all-H utterances. Figure 11 presents averaged time normalized pitch contour of an all-L utterance. The gradual lowering of f₀ in the IP shows that pitch gradually drops to a lower level before it finally undergoes a steep fall. Figure 12 presents the downward f₀ trajectory of Maxf₀ for H tones of the all-H utterance. This is compared with the downward slope of Mean f₀ of L tones of the all-L utterance. It can be seen that for the all-H utterance, the f₀ falls from a higher peak to a lower f₀ target aligned to the final tone when compared to the f₀ slope of the all-L utterance. Table 4 compares the amount of f₀ drop for the non-initial tonal targets in both the all-H and all-L sentences. It can be seen that non-initial H tones in the all-H sentence undergo greater amount of pitch drop than non-initial L tones in the all-L sentence.

The trend lines for downward pitch movement presented in Figure 11 also provide evidence for two kinds of downtrends in Boro insofar as pitch drop is concerned. Downstepping in Boro results in greater amount of f₀ lowering than the lowering attested in declination. Figure 11 presents an instance of final-lowering in Boro as the pitch contour drops to the lowest level towards the last part of the final syllable /dɯ̀ŋ/ ‘PRF’.

Initial occurrences of words with L tones in Boro are marked by a rise followed by a fall, although in citation forms L tones in Boro manifest phonetically by falling f₀ movement. Figure 10 presents the time normalized pitch contour of a sentence with /àŋ/ ‘I’ occurring in IP initial position. f₀ shapes of the L tone words vary when they occur in phrase initial position. An instance of it can be seen in the L tone word /àŋ/ ‘I’ which surfaces with an upward movement of the pitch followed by gradual drop of f₀ at the end of the coda consonant. This shows the robust nature of this initial contour in Boro as far as lexical low tone in the language is concerned.

Additionally, a comparison of the nature of distribution of these between initial and non-initial occurrences of L tones, and between initial occurrences of H and L tones in Boro is quite important for understanding the nature of f₀ movement for IP initial tones. Figure 13 presents pitch tracks of IPs with H and L tones occurring in the subject positions. It can be seen on the left panel of Figure 13 that the initial word /dɯì-ao/ ‘water-LOC’ surfaces with a rise aligned to the middle of the second syllable followed by a fall to a low target at the end of the suffix. The IP initial H tone also surfaces with a rising contour. The pitch contour in Figure 13 shows an IP with /bí-ɯ/ ‘he-NOM’ occurring initially in the right panel. In /bí-ɯ/ ‘he-NOM’ The High tone rises to a peak aligned to the second syllable. This rise in f₀ is characteristic of rising f₀ trends in Boro H tones. Thus the two panels of Figure 13 show that both the contrastive lexical tones occurring IP initially, surface with a rising pitch. The only noticeable difference is in the scaling of the targets. In the instance of /bí-ɯ/ ‘he-NOM’ the f₀ reaches a higher target. The high target for the f₀ rise of /dɯì-ao/ ‘water-LOC’ is scaled lower. This rise is consistently seen in all the other sentences in the dataset. It is also seen that the rise in f₀ affecting the initial L tone does not extend to the second L tone if there is one. The upper panel of Figure 14 shows the pitch track of an IP with a sequence of initial L tones in /ɡudùŋ dɯì/ ‘hot water’. It can be seen that the high target of the rising contour aligns to the surface TBU in /ɡudùŋ/ ‘hot’ and the second L tone aligned to /dɯì/ ‘water’ surfaces with the characteristic falling contour. Thus, where there’s an LL sequence of initial tones, the high target for the rising contour aligns to the first L tone. The f₀ trend of the initial sequence of LL tones in /ɡudùŋ dɯì/ ‘hot water’ can be compared with that of its medial occurrence presented in the lower panel of Figure 14. In the medial occurrence, the sequence of LL tones surface with a continuous fall as can be seen for /ɡudùŋdɯì/ ‘hot water’ in the lower panel of Figure 14. Despite the presence of the initial monosyllabic constituent (/àŋ/ ‘I’) or disyllabic (/ɡudùŋ/ ‘hot’) the L tone surfaces with a rising f₀ contour. In the case of a disyllabic constituent like /ɡudùŋ/ ‘hot’, the high target for the rising f₀ trend aligns to the second syllable. Despite their scaling differences, both H tones and L tones in Boro surface with a rising contour.

The left panel of Figure 15 presents the pitch contour of a sentence with a monosyllabic word with H tone occurring initially. In the right panel of Figure 15, a disyllabic word with H tone occurs initially. It can be seen that both the monosyllabic /nɯ́ŋ/ ‘you’ and the disyllabic /nɯ́ŋní/ ‘you-POSS’ surfaces with a rise in f₀. The peak of the f₀ rise aligns to the second syllable in /nɯ́ŋní/ ‘you-POSS’ and to the final segment of the first syllable in /nɯ́ŋ/ ‘you’.

Another important aspect of IP initial pitch rise is highlighted by the left panel in Figure 16. It presents the pitch contour of an utterance with an initial LH sequence. The initial L tone aligned to the second syllable of /ɡizì/ ‘torn’ surfaces with a high target. The pitch contours of the initial occurrence of /ɡizì/ ‘torn’ and that of its medial occurrence presented in the right panel of Figure 16 shows this comparison. But the high target for the f₀ rise of the IP initial L tone in /ɡizì/ ‘torn’ is scaled lower than the one found in the case of an IP initial H tone. The lines in Figure 16, and the rest of the discussion here, refer to f₀ heights aligned to a particular syllable. In other words, there exists a difference of scaling between the high target aligned to /ɡizì/ ‘torn’ and that of the lexical H tone aligned to the second syllable of bí-ɯ ‘he-NOM’.

Higher f0 target at the beginning of an utterance in non-tonal languages has been grammaticalized by proposing an H% initial boundary tone in English (Pierrehumbert 1980). Complex boundary tones consisting of a tone sequence can also occur at the left edge of prosodic units. The LHLH string marking accentual phrase is Seoul Korean is reduced to just an initial LH if the accentual phrase consists of three syllables (Jun 1993; 1998). Accentual phrases in Northern Bizkalan Basque are characterized by an initial pitch rise due to a sequence of LH tones where the target L occurs on the first syllable and the H aligns to the second syllable (Gussenhoven 2004). This is similar to what Pierrehumbert & Beckman (1988) proposes for Tokyo Japanese: the final L boundary tone of an accentual phrase surfaces on the next accentual phrase beginning with a H target. This results in an initial rise for the following accentual phrase and this rise is attributed to the sequence of LH initial boundary tone. In Northern Bizkalan Basque the realization of the LH initial boundary sequence depends on the availability of syllables.

The initial rising f₀ contour in Boro can also be interpreted as an initial LH% boundary tone. This left edge boundary tone interacts differently with the two contrastive tones in Boro. It influences the IP initial L tone in such a way that the tone surfaces with a rising contour. An instance of it is presented in the way /àŋ/ ‘I’ surfaces in Figure 20. The f₀ for the H% of the boundary LH% is scaled lower than that of the high target for an IP initial H tone. The comparison between the pitch contours for /dɯì-ao/ ‘water-LOC’ and /bí-ɯ/ ‘he-NOM’ in Figure 11 illustrates this aspect of intonation in Boro. The H% of the boundary LH% also does not cause downstepping of the following lexical H tone. The sequence of the boundary LH% and lexical H tones aligned to /ɡizì zí/ ‘torn shirt’ in Figure 16 shows it. It can be seen in Figure 16 that the L of the boundary LH% aligns to the first syllable of /ɡizì/ ‘torn’ and the H% surfaces aligned to the second syllable. Following this, the pitch is raised to an even higher target for the lexical H aligned to /zí/ ‘shirt’. The alignment schema presented in 17 shows how LH% is squeezed when it is associated with a monosyllabic stem with L tone like /àŋ/ ‘I’. When the boundary LH% associates with a disyllabic word with L tone, L aligns to the first syllable and H% aligns to the second syllable. LH% interacts with the initial H tone in such a way that the H% does not surface. This is irrespective of the number of syllables of the initial constituent. The alignment schema for /nɯ́ŋ/ ‘you’ and /nɯ́ŋní/ ‘you-POSS’, presented in Figure 16.

The LH% sequence does spread to a second L tone following the one occurring on the left edge of the IP. The pitch contour for /ɡudùŋ dɯì lɯ̀ŋnaiá dehàní tʰakaì mɯzàŋ/ ‘To have warm water is good for health’ in Figure 13 illustrates this. The H target for the LH% aligns to the second syllable of the word /ɡudùŋ/ ‘warm’ and the following word /dɯì/ ‘water’ surfaces with the characteristic falling f₀ trend for Boro L tones. Since the initial high tone preempts the occurrence of the H%, only L surface IP initially on a preceding H tone. Evaluation of the pitch contours in Figure 13 through Figure 16 shows that the high tone differs from the high target for initial LH% in terms of scaling.

The ip in Boro is sometimes comprised of a clause or an adjectival phrase or in some other cases a pre-posed focus phrase. The evidence for the existence for the level of the intermediate phrase in Boro comes from the perspectives of (a) weaker disjuncture marking edges of non-final constituents larger than the PrWd and smaller than IP and (b) suspension of lowering of pitch targets for non-initial H tones. We find substantial instances of occurrences of both weak disjuncture and suspension of lowering of non-initial H tones in Boro.

If the argument for the existence of ip as a prosodic constituent stems from the realization of weaker disjunctures between two adjacent clauses, then the edges of ips in Boro proffer sufficient examples. The tones marking the edges of such ips in Boro do not show the same magnitude of pitch range modification as found in the case of IP right edge tones. IPs in Boro are characterized by a bigger inventory of right edge boundary marking tones than that is found in the case of ips.7 Only non-final ips in Boro surface with their ip boundary tones. The boundary tones of the final ips get overridden by the final boundary tone of the IP. Figure 17 presents an instance of this.

The pitch contour of the sentence /bibríá mitʰiɡoɯ́di sɯ̀r daodɯí baìdɯŋmɯn/ ‘Bibari knows who bought eggs’ shows that the sentence consists of two ips forming an IP. The first ip, including the complementizer /di/ ‘that’, ends with an HL- ip boundary tone. Figure 18 shows how the pitch contour of the ip boundary tone exhibits a rise and a subsequent fall during the ip final syllable. The f₀ fall for HL- ip boundary tone is not realized in the same manner when the falling contour marks the edge of an IP. The right panel of Figure 18 presents the pitch contour of an IP with the boundary HL tone occurring in its right edge. A comparison between the pitch tracks shows that the HL boundary tone is realized differently depending on whether it aligns to the right edge of an ip or IP. The boundary tone of the second ip gets influenced by the L% IP boundary tone in the left panel of Figure 18 and the f₀ falls to a low target.

The second argument in favour of the ip level in Boro is based on the nature of pitch curves noticed in the case of some utterances. Section 4.2 has already presented evidence to show that in an IP consisting of H lexical tones, the non-initial ones undergo downstepping. The prosodic requirement of each of the final H tones within a series of non-initial PrWds undergoing pitch drop is violated in Boro IPs beginning with a nominative clause. The final tone of the nominative clause functioning as Subject NP does not affect the following H tone, and the latter surfaces with a higher pitch target than the earlier one. There are instances in the literature where suspension of downstepping has been interpreted as evidence for marking a prosodic boundary in the study of intonation. Guessenhoven (2004), based on evidence from Poser (1984), Pierrehumbert and Beckman (1988) and Kubozono (1992), informs that in Tokyo Japanese the ip is the domain of downstep. The pitch contours presented in Figure 17 also show that downstepping is blocked after the nominative clauses due to a prosodic boundary.

In the left panel of Figure 19, the second H tone in the nominative clause /daodɯí zánaiá/ ‘to eat egg’ undergoes downstepping. But the third H tone aligned to the adjective /zɯbɯ́d/ ‘very’ surfaces higher than the preceding H tone. The mean of maximum f₀ (Maxf₀) of the final vowel in /zánai-á/ ‘to eat’ is 169.67 Hz (n = 20) compared to 175.10 Hz of that of the final vowel in /zɯbɯ́d/ ‘very’. The ip boundary after the second H lexical tone blocks the downstepping of the third H lexical tone. The lengthened nominative clause in the right panel of Figure 19 also functions as a distinct prosodic unit. The nominative clause in the right panel of Figure 19 ends with a H lexical tone and the next lexical H tone is not downstepped. The mean of maximum f₀ (Maxf₀) of the final vowel in /zánai-á/ ‘to eat’ in the sentence /enzòrní bedòr zánaiá maozíní tʰakaì mɯzàŋ/ ‘It is good for cat to eat rat meat’ is 158.19 Hz (n = 20) compared to 168.81 Hz of that of the final vowel in /maozíní/ ‘cat-POSS’ in the same sentence. Figure 20 presents the comparison of Maxf₀ between two adjacent H lexical tones separated by ip boundaries. Based on the evidence presented above we surmise that suspension of downstepping in Boro is a prosodic cue for ips. Effectively, this results in the blocking of downstepping across ip boundaries.

Fronted and other topicalized constituents are often highlighted by intonational markers, such as pause or a boundary tone (Frascarelli 2000). Although the canonical word order in Boro is Subject + Object + Verb, it allows the object to be preposed to the initial position of a sentence for ex-situ focus marking. Noun phrases, which are thus placed sentence initially for ex-situ object focus (Kügler & Genzel 2013), also form ips in Boro. Figure 21 presents an instance of such kind of ex-situ focus marking where the object noun phrase /daodɯí/ ‘egg’ occurs sentence initially.

As can be seen in Figure 21, the right aligned H tone of the object is realized within the last syllable of the focused constituent and it is followed by an L ip boundary tone. The evidence for the preposed object forming an ip can be attributed to the existence of downstepping in Boro. In Figure 21, with two lexical H tones in the first two words of /daodɯí-kʰoú bí-ɯ baìdɯŋ-mɯn/ ‘EGG he bought’, the second H is realized with higher f₀ target than the first one. This evidence also suggests that downstepping is not applied across ips in Boro. As the pre-focused constituent /daodɯí-kʰoú/ ‘egg-ACC’ is followed by an ip boundary, the following H tone in bíɯ ‘he-NOM’ is not downstepped. This suggest that ip is the domain of downstepping in Boro. Figure 22 presents another instance of an IP with a preposed object receiving ex-situ focus.

The pitch contour presented in Figure 22 is of a sentence consisting of a direct and an indirect object with a di-transitive verb. This Figure shows that the second H tone surfaces with a higher f₀ target than the first one, thus negating any pitch drop for downstepping. The initial PrWd /tʰaizoú-kʰoú/ ‘mango-ACC’ is followed by an ip boundary. The second ip in Figure 22 follows the characteristic downstepping of non-initial H tones. The H tone in /bibarí-nɯ/ ‘Bibari-DAT’ surfaces lower than the ip initial H tone in /bí-ɯ/ ‘he-NOM’. Downstepping of non-initial H tones within an ip domain can also be seen in preposed constituents with additional H lexical tones. Figure 23 presents the pitch contour of a longer IP.

In Figure 23, constituents in the pre-posed object /tʰaisé tʰaizoú/ ‘one mango’ have lexical H tones and the second H tone undergoes a pitch level drop. The pitch again rises to a high target for the third H followed by a downstepped H tone. The ip prosodic boundary after the preposed object /tʰaisé tʰaizoú/ ‘one mango’ prohibits the percolation of downstepping to the next H tone in /bibarí-ní/ ‘Bibari POSS’. However the second H tone in the second ip in Figure 23 undergoes downstepping. The H tone in /pʰisazɯ́-á/ ‘daughter-NOM’ appears lower than that of /bibarí-ní/ ‘Bibari POSS. This shows that the domain of downstepping can be a prosodically determined domain and crucial for the operation of sentence level prosody in Boro.