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Tone is the use of pitch in language to distinguish lexical or grammatical meaning – that is, to distinguish or to inflect words. All verbal languages use pitch to express emotional and other paralinguistic information and to convey emphasis, contrast, and other such features in what is called intonation, but not all languages use tones to distinguish words or their inflections, analogously to consonants and vowels. Such tonal phonemes are sometimes called tonemes [ˈtəʊniːm], where each toneme is a lexically distinct variant of the same phoneme, that is phonetically distinguished from other tonemes only by the tone of the vowel. Tonal languages are extremely common in Africa, East Asia, and Central America, but rare elsewhere in Asia and in Europe; as many as seventy percent of world languages may be tonal.
In many tonal African languages, such as most Bantu languages, tones are distinguished by their pitch level relative to each other, known as a register tone system. In multi-syllable words, a single tone may be carried by the entire word, rather than a different tone on each syllable. Often grammatical information, such as past versus present, "I" versus "you", or positive versus negative, is conveyed solely by tone.
In the most widely-spoken tonal language, Mandarin Chinese, tones are distinguished by their distinctive shape, known as contour, with each tone having a different internal pattern of rising and falling pitch. Words are often monosyllabic, and many words are differentiated solely by tone; in a multisyllabic word each syllable often carries its own tone. Unlike in Bantu systems, tone plays little role in modern Chinese grammar, though the tones descend from features in Old Chinese that did have morphological significance (e.g. changing a verb to a noun or vice-versa).
Contour systems are typical of languages of the Mainland Southeast Asia linguistic area, including Tai–Kadai, Vietic and Sino-Tibetan languages. The Afroasiatic, Khoisan, Niger-Congo and Nilo-Saharan languages spoken in Africa are dominated by register systems. Some languages combine both systems, such as Cantonese, which produces three varieties of contour tone at three different pitch levels, or the Omotic (Afroasiatic) language Bench, which employs five level tones and one or two rising tones across levels.
Many languages use tone in a more limited way. In Japanese, fewer than half of the words have drop in pitch; words contrast according to which syllable this drop follows. Such minimal systems are sometimes called pitch accent, since they are reminiscent of stress accent languages, which typically allow one principal stressed syllable per word. However, there is debate over the definition of pitch accent, and whether a coherent definition is even possible.
Most languages of sub-Saharan Africa are members of the Niger-Congo family, which is predominantly tonal; notably excepting Swahili (in the Southeast), most languages spoken in the Senegambia (among them Wolof, Serer and Cangin languages), Koyra Chiini and Fulani. The Afroasiatic languages include both tonal (Chadic, Omotic) and nontonal (Semitic, Berber, Egyptian, and most Cushitic) branches.
There are numerous tonal languages in East Asia and South East Asia. Most Sino-Tibetan languages including all the Chinese languages (though some such as Shanghainese are only marginally tonal), Lhasa Tibetan and Burmese are tonal, as are a few Austroasiatic languages such as Vietnamese, Tai-Kadai languages including Thai, and Lao, and Austronesian languages Cemuhi. However, some members of these families are also nontonal including Amdo Tibetan, Khmer and Malay. Other languages represented in the region, such as Mongolian, Uyghur and Japanese belong to language families that do not contain any tonality as defined here.
A few languages outside these major groups have tonality, including Lahnda, Punjabi and Ancient Greek, which are Indo-European languages. Although the Austronesian language family has some tonal members, no tonal languages have been discovered in Australia.
A large number of North, South and Central American languages are tonal, including many of the Athabaskan languages of Alaska and the American Southwest (including Navajo), and the Oto-Manguean languages of Mexico. Among the Mayan languages, which are mostly non-tonal, Yucatec (with the largest number of speakers), Uspantek, and one dialect of Tzotzil have developed tone systems. However, although tone systems have been recorded for many American languages, little theoretical work has been completed for the characterization of their tone systems. In different cases, Central American tone languages have been found to possess tone systems similar to both Asian and African tone languages.
Languages that are tonal include:
In some cases it is difficult to determine whether a language is tonal. For example, the Ket language has been described as having up to eight tones by some investigators, as having four tones by others, but by some as having no tone at all. In cases such as these, the classification of a language as tonal may depend on the researcher's interpretation of what tone is. For instance, the Burmese language has phonetic tone, but each of its three tones is accompanied by a distinctive phonation (creaky, murmured or plain vowels). It could be argued either that the tone is incidental to the phonation, in which case Burmese would not be phonemically tonal, or that the phonation is incidental to the tone, in which case it would be considered tonal. Something similar appears to be the case with Ket.
Most languages use pitch as intonation to convey prosody and pragmatics, but this does not make them tonal languages. In tonal languages, each syllable has an inherent pitch contour, and thus minimal pairs (or larger minimal sets) exist between syllables with the same segmental features but different tones.
Here is a minimal tone set from Mandarin Chinese, which has five tones, here transcribed by diacritics over the vowels:
These tones combine with a syllable such as "ma" to produce different words. A minimal set based on "ma" are, in pinyin transcription,
These may be combined into the rather contrived sentence,
A well-known tongue-twister in the Standard Thai and Standard Lao is:
Vietnamese has its version: Bấy nay bây bầy bảy bẫy bậy.
Tone is most frequently manifested on vowels, but in most tonal languages where voiced syllabic consonants occur they will bear tone as well. This is especially common with syllabic nasals, for example in many Bantu and Kru languages, but also occurs in Serbo-Croatian.
Tones can interact in complex ways through a process known as tone sandhi.
Tone systems fall into two broad patterns, according to whether contour tones exist.
Most Chinese languages use contour tone systems, where the distinguishing feature of the tones are their shifts in pitch (that is, the pitch is a contour), such as rising, falling, dipping, or level. Most Bantu languages, on the other hand, have non-contour tone (or register tone) systems where the distinguishing feature is the relative difference between the pitches, such as high, mid, or low, rather than their shapes. In such systems there is a default tone, usually low in a two-tone system or mid in a three-tone system, that is more common and less salient than other tones. There are also languages that combine relative-pitch and contour tones, such as many Kru languages, where nouns are distinguished by contour tones and verbs by pitch. Others, such as Yoruba, have phonetic contours, but these can easily be analysed as sequences of single-pitch tones, with for example sequences of high–low /áà/ becoming falling [âː], and sequences of low–high /àá/ becoming rising [ǎː].
Falling tones tend to fall further than rising tones rise; high–low tones are common, whereas low–high tones are quite rare. A language with contour tones will also generally have as many or more falling tones than rising tones. However, exceptions are not unheard of; Mpi, for example, has three level and three rising tones, but no falling tones.
Lexical tones more complex than dipping (falling–rising) or peaking (rising–falling) are quite rare, perhaps nonexistent, though prosody may produce such effects. However, the Old Xiang dialect of Qiyang is reported to have two "double contour" lexical tones, high and low fall–rise–fall, or perhaps high falling – low falling and low falling – high falling: ˦˨˧˨ and ˨˩˦˨ (4232 and 2142).
In a number of East Asian languages, tonal differences are closely intertwined with phonation differences. In Vietnamese, for example, the ngã and sắc tones are both high-rising but the former is distinguished by having a glottal stop in the middle. Similarly, the nặng and huyền tones are both low-falling, but the nặng tone is shorter and pronounced with creaky voice at the end, while the huyền tone is longer and often has breathy voice. In some languages, such as Burmese, pitch and phonation are so closely intertwined that the two are combined in a single phonological system, where neither can be considered without the other. Confusingly, such systems are termed register, which is unrelated to "register tone" as described above.
Tones are realized as pitch only in a relative sense. 'High tone' and 'low tone' are only meaningful relative to the speaker's vocal range and in comparing one syllable to the next, rather than as a contrast of absolute pitch such as one finds in music. As a result, when one combines tone with sentence prosody, the absolute pitch of a high tone at the end of a prosodic unit may be lower than that of a low tone at the beginning of the unit, because of the universal tendency (in both tonal and non-tonal languages) for pitch to decrease with time in a process called downdrift.
Tones may affect each other just as consonants and vowels do. In many register-tone languages, low tones may cause a downstep in following high or mid tones; the effect is such that even while the low tones remain at the lower end of the speaker's vocal range (which is itself descending due to downdrift), the high tones drop incrementally like steps in a stairway or terraced rice fields, until finally the tones merge and the system has to be reset. This effect is called tone terracing.
Sometimes a tone may remain as the sole realization of a grammatical particle after the original consonant and vowel disappear, so it can only be heard by its effect on other tones. It may cause downstep, or it may combine with other tones to form contours. These are called floating tones.
In many contour-tone languages, one tone may affect the shape of an adjacent tone. The affected tone may become something new, a tone that only occurs in such situations, or it may be changed into a different existing tone. This is called tone sandhi. In Mandarin Chinese, for example, a dipping tone between two other tones is reduced to a simple low tone, which otherwise does not occur in Mandarin Chinese, whereas if two dipping tones occur in a row, the first becomes a rising tone, indistinguishable from other rising tones in the language. For example, the words 很 [xɤn˨˩˦] 'very' and 好 [xaʊ˨˩˦] 'good' produce the phrase 很好 [xɤn˧˥ xaʊ˨˩˦] 'very good'.
Another difference between tonal languages is whether the tones apply independently to each syllable or to the word as a whole. In Cantonese, Thai, and to some extent the Kru languages, each syllable may have a tone, whereas in Shanghainese, the Scandinavian languages, and many Bantu languages, the contour of each tone operates at the word level. That is, a trisyllabic word in a three-tone syllable-tone language has many more tonal possibilities (3 × 3 × 3 = 27) than a monosyllabic word (3), but there is no such difference in a word-tone language. For example, Shanghainese has two contrastive tones no matter how many syllables are in a word. Many languages described as having pitch accent are word-tone languages.
Tone sandhi is an intermediate situation, as tones are carried by individual syllables, but affect each other so that they are not independent of each other. For example, a number of Mandarin Chinese suffixes and grammatical particles have what is called (when describing Mandarin Chinese) a "neutral" tone, which has no independent existence. If a syllable with a neutral tone is added to a syllable with a full tone, the pitch contour of the resulting word is entirely determined by that other syllable:
|Tone in isolation||Tone pattern with|
added 'neutral tone'
|rising ˧˥||˧˥.˧||伯伯||bóbo||elder uncle|
After high level and high rising tones, the neutral syllable has an independent pitch that looks like a mid-register tone – the default tone in most register-tone languages. However, after a falling tone it takes on a low pitch; the contour tone remains on the first syllable, but the pitch of the second syllable matches where the contour leaves off. And after a low-dipping tone, the contour spreads to the second syllable: the contour remains the same (˨˩˦) whether the word has one syllable or two. In other words, the tone is now the property of the word, not the syllable. Shanghainese has taken this pattern to its extreme, as the pitches of all syllables are determined by the tone before them, so that only the tone of the initial syllable of a word is distinctive.
Languages with simple tone systems or pitch accent may have one or two syllables specified for tone, with the rest of the word taking a default tone. Such languages differ in which tone is marked and which is the default. In Navajo, for example, syllables have a low tone by default, while marked syllables have high tone. In the related language Sekani, however, the default is high tone, and marked syllables have low tone. There are parallels with stress: English stressed syllables have a higher pitch than unstressed syllables, whereas in Russian, stressed syllables have a lower pitch.
In East Asia, tone is typically lexical. This is characteristic of heavily tonal languages such as Chinese, Vietnamese, Thai, and Hmong. That is, tone is used to distinguish words which would otherwise be homonyms, rather than in the grammar, though some Yue Chinese dialects have minimal grammatical use of tone. (In Old Chinese, tones may have grammatical functions.) However, in many African languages, especially in the Niger–Congo family, tone is crucial to the grammar, with relatively little lexical use. In the Kru languages, a combination of these patterns is found: nouns tend to have complex tone systems reminiscent of East Asia, but are not much affected by grammatical inflections, whereas verbs tend to have simple tone systems of the type more typical of Africa, which are inflected to indicate tense and mood, person, and polarity, so that tone may be the only distinguishing feature between 'you went' and 'I won't go'. In colloquial Yoruba, especially when spoken quickly, vowels may assimilate to each other, and consonants elide, so that much of the lexical and grammatical information is carried by tone. In languages of West Africa such as Yoruba, people may even communicate with so-called "talking drums", which are modulated to imitate the tones of the language, or by whistling the tones of speech.
Note that tonal languages are not distributed evenly across the same range as non-tonal languages. Instead, the majority of tone languages belong to the Niger-Congo, Sino-Tibetan and Vietic groups, which are then composed by a large majority of tone languages and dominate a single region. Only in limited locations—South Africa, New Guinea, Mexico, Brazil and a few others do tone languages seem to occur as individual members or small clusters within a non-tone dominated area. In some locations, like Central America, this may represent no more than an incidental effect of which languages were included when examining distribution; for groups like Khoi-San in Southern Africa and Papuan languages, whole families of languages possess tonality, but simply have relatively few members, while for some North American tone languages multiple independent origins are suspected.
If generally considering only complex-tone vs. no-tone it might be concluded that tone is almost always an ancient feature within a language family that is highly conserved among members. However, when considered in addition to 'simple' tone systems that include only two tones, tone as a whole appears to be more labile, appearing several times within Indo-European, several times in American languages, and several times in Papuan families. This may indicate that rather than a trait unique to some language families, tone is a latent feature of most language families that may more easily arise and disappear as languages change over time.
There are three main approaches to notating tones in phonetic descriptions of a language.
|Name||Top tone||High tone||Mid tone||Low tone||Bottom tone||Falling tone||High falling tone||Low falling tone||Rising tone||High rising tone||Low rising tone||Dipping tone|
In African linguistics (as well as in many African orthographies), usually a set of accent marks is used to mark tone. The most common phonetic set (which is also included in the International Phonetic Alphabet) is found below:
Several variations are found. In many three-tone languages, it is common to mark High and Low tone as indicated above, but to omit marking of the Mid tone, e.g., má (High), ma (Mid), mà (Low). Similarly, in some two-tone languages, only one tone is marked explicitly.
With more complex tonal systems, such as in the Kru and Omotic languages, it is usual to indicate tone with numbers, with 1 for HIGH and 4 or 5 for LOW in Kru, but 1 for LOW and 5 for HIGH in Omotic. Contour tones are then indicated 14, 21, etc.
In the Chinese tradition, numerals are assigned to various tones (see Tone number). For instance, Standard Mandarin Chinese, the official language of China has four lexically contrastive tones, and the numerals 1, 2, 3, and 4 are assigned to four tones. Syllables can sometimes be toneless and are described as having a neutral tone, typically indicated by omitting tone markings. Chinese dialects are traditionally described in terms of four tonal categories ping 'level', shang 'rising', qu 'exiting', ru 'entering', based on the traditional analysis of Middle Chinese (see Four tones); note that these are not at all the same as the four tones of modern standard Mandarin Chinese. Depending on the dialect, each of these categories may then be divided into two tones, typically called yin and yang. Typically, syllables carrying the ru tones are closed by voiceless stops in Chinese dialects that have such coda(s), so that, in such dialects, ru is not a tonal category in the sense used by Western linguistics, but rather a category of syllable structures. Chinese phonologists perceived these checked syllables as having concomitant short tones, justifying them as a tonal category. During the period of Middle Chinese, when the tonal categories were established, the shang and qu tones also had characteristic final obstruents with concomitant tonic differences, whereas syllables bearing the ping tone ended in a simple sonorant. An alternate to using the Chinese category names is to assign to each category a numeral ranging from 1–8, or sometimes higher for some Southern Chinese languages with additional tone splits. It should be noted that syllables belonging to the same tone category differ drastically in actual phonetic tone across the Chinese languages even amongst sub-dialects of the same language/dialect group. For example, the yin ping tone is a high level tone in Beijing Mandarin Chinese, but a low level tone in Tianjin Mandarin Chinese.
More iconic systems use tone numbers, or an equivalent set of graphic pictograms known as 'Chao tone letters'. These divide the pitch into five levels, with the lowest being assigned the value 1, and the highest the value 5. (This is the opposite of equivalent systems in Africa and the Americas.) The variation in pitch of a tone contour is notated as a string of two or three numbers. For instance, the four Mandarin Chinese tones are transcribed as follows (note that the tone letters will not display properly unless you have a compatible font installed):
|High tone||55||˥||(Tone 1)|
|Mid rising tone||35||˧˥||(Tone 2)|
|Low dipping tone||214||˨˩˦||(Tone 3)|
|High falling tone||51||˥˩||(Tone 4)|
A mid-level tone would be indicated by /33/, a low level tone /11/, etc. The doubling of the number is commonly used with level tones to distinguish them from tone numbers; tone 3 in Mandarin Chinese, for example, is not mid /3/. However, this is not necessary with tone letters, so /33/ = simple /˧/.
IPA diacritic notation is also sometimes seen for Chinese. One reason it is not more widespread is that only two contour tones, rising /ɔ̌/ and falling /ɔ̂/, are widely supported by IPA fonts, while several Chinese languages have more than one rising or falling tone. One common work-around is to retain standard IPA /ɔ̌/ and /ɔ̂/ for high-rising (/35/) and high-falling (/53/) tones, and to use the subscript diacritics /ɔ̗/ and /ɔ̖/ for low-rising (/13/) and low-falling (/31/) tones.
Standard Central Thai has five tones: high, mid, low, rising and falling. The Thai written script is an alphasyllabary which specifies the tone unambiguously. Tone is indicated by an interaction of the initial consonant of a syllable, the vowel length, the final consonant (if present), and sometimes a tone mark. A particular tone mark may denote different tones depending on the initial consonant.
Vietnamese uses the Latin alphabet, and the 6 tones are marked by diacritics above or below a certain vowel of each syllable. In many words that end in diphthongs, however, exactly which vowel is marked depends on the writer's style. Notation for Vietnamese tones are as follows:
|ngang||mid level, ˧||not marked||a|
|huyền||low falling, ˨˩||grave accent||à|
|sắc||high rising, ˧˥||acute accent||á|
|hỏi||dipping, ˧˩˧||hook above||ả|
|ngã||creaky rising, ˧ˀ˥||tilde||ã|
|nặng||creaky falling, ˨˩ˀ||dot below||ạ|
The Latin-based Hmong and Iu Mien alphabets use full letters for tones. In Hmong, one of the eight tones (the ˧ tone) is left unwritten, while the other seven are indicated by the letters b, m, d, j, v, s, g at the end of the syllable. Since Hmong has no phonemic syllable-final consonants, there is no ambiguity. This system enables Hmong speakers to type their language with an ordinary Latin-letter keyboard without having to resort to diacritics. In the Iu Mien, the letters v, c, h, x, z indicate tones but, unlike Hmong, it also has final consonants written before the tone.
Several North American languages have tone, one of which is Cherokee, an Iroquoian language. Oklahoma Cherokee has six tones (1 low, 2 medium, 3 high, 4 very high, 5 rising and 6 falling).
In Mesoamericanist linguistics, /1/ stands for high tone and /5/ stands for low tone, except in Oto-Manguean languages, where /1/ may be low tone and /3/ high tone. It is also common to see acute accents for high tone and grave accents for low tone and combinations of these for contour tones. Several popular orthographies use 〈j〉 or 〈h〉 after a vowel to indicate low tone Southern Athabascan languages that include the Navajo and Apache languages are tonal, and are analyzed as having 2 tones, high and low. One variety of Hopi has developed tone, as has the Cheyenne language.
The Mesoamerican language stock called Oto-Manguean is famously tonal and is the largest language family in Mesoamerica, containing languages including Zapotec, Mixtec, and Otomí, some of which have as many as five register tones (Trique, Usila Chinantec) and others only two (Matlatzinca and Chichimeca Jonaz). Other languages in Mesoamerica that have tones are Huichol, Yukatek Maya, the Tzotzil of San Bartolo, Uspanteko, and one variety of Huave.
A number of languages of South America are tonal. For example, various analyses of the Pirahã language describe either two or three tones. The Ticuna language isolate is exceptional for having five register tones (the only other languages in America to have such a system are Trique and Usila, mentioned above).
|This section requires expansion. (June 2008)|
Both Swedish and Norwegian have simple word tone systems, often called pitch accent (although they are actually contour tones), that only appears in words of two or more syllables. Each word has a lexical tone, which varies by dialect. Words whose pronunciation differs only in tone are frequently morphologically or etymologically unrelated, and may be spelled differently, as in Norwegian cider ‘cider’ versus sider ‘pages’. The two word tones are conventionally called toneme 1 and toneme 2 in Norway and acute accent and grave accent in Sweden. In Norway, there are two major dialectal divisions based on tone, roughly eastern and western/northern, where the tones have different values: in the east, T1 = level low, T2 = falling; in the west/north, T1 = falling, T2 = rising-falling.
In Limburgish and the Franconian dialects of Germany, tones can also occur in monosyllabic words, e.g., Limb. dáág ‘day’ (singular), dáàg ‘days’ (plural). Limburgish is typically a 2-tone system, distinguishing between level high and falling, but these tones can be realized in other ways depending on syntax, and some vowels diphthongize or monophthongize under certain tones. Latvian has 2-, 3- or 4-tone system depending on the dialect.
In practical alphabetic orthographies, a number of approaches are used. Diacritics are common, as in pinyin, though these tend to be omitted. Thai uses a combination of redundant consonants and diacritics. Tone letters may also be used, for example in Hmong RPA and several minority languages in China. Or tone may simply be ignored. This is possible even for highly tonal languages: for example, the Chinese navy has successfully used toneless pinyin in government telegraph communications for decades, and likewise Chinese reporters abroad may file their stories in toneless pinyin. Dungan, a variety of Mandarin Chinese spoken in Central Asia, has, since 1927, been written in orthographies that do not indicate tone. Ndjuka, where tone is less important, ignores tone except for a negative marker. However, the reverse is also true: in the Congo, there have been complaints from readers that newspapers written in orthographies without tone marking are insufficiently legible.
Languages may distinguish up to five levels of pitch, though the Chori language of Nigeria is described as distinguishing six surface tone registers. Since tone contours may involve up to two shifts in pitch, there are theoretically 5 × 5 × 5 = 125 distinct tones for a language with five registers. However, the most that are actually used in a language is a tenth of that number.
Several Kam–Sui languages of southern China have nine contrastive tones, including contour tones. For example, the Kam language has 9 tones: 3 more-or-less fixed tones (high, mid and low); 4 unidirectional tones (high and low rising, high and low falling); and 2 bidirectional tones (dipping and peaking). This assumes that checked syllables are not counted as having additional tones, as they traditionally are in China: For example, in the traditional reckoning, the Kam language has 15 tones, but 6 occur only in syllables closed with /p/, /t/ or /k/ while the other 9 occur in syllables not ending in one of these sounds. Preliminary work on the Wobe language of Liberia and Côte d'Ivoire, and the Chatino languages of southern Mexico suggests that some dialects may distinguish as many as fourteen tones, but many linguists have expressed doubts, believing that many of these will turn out to be sequences of tones or prosodic effects.
|Sound change and alternation|
André-Georges Haudricourt established that Vietnamese tone originated in earlier consonantal contrasts, and suggested similar mechanisms for Chinese. It is now widely held that Old Chinese did not have phonemically contrastive tone. The historical origin of tone is called tonogenesis, a term coined by James Matisoff. Tone is frequently an areal rather than a genealogical feature. That is, a language may acquire tones through bilingualism if influential neighboring languages are tonal, or if speakers of a tonal language shift to the language in question, and bring their tones with them. In other cases, tone may arise spontaneously, and surprisingly quickly: the dialect of Cherokee in Oklahoma has tone, but the dialect in North Carolina does not, although they were only separated in 1838.
Very often, tone arises as an effect of the loss or merger of consonants. (Such trace effects of disappeared tones or other sounds have been nicknamed Cheshirisation, after the lingering smile of the disappearing Cheshire Cat in Alice in Wonderland.) In a non-tonal language, voiced consonants commonly cause following vowels to be pronounced at a lower pitch than other consonants do. This is usually a minor phonetic detail of voicing. However, if consonant voicing is subsequently lost, that incidental pitch difference may be left over to carry the distinction that the voicing had carried, and thus becomes meaningful (phonemic). This is seen historically in Panjabi: the Panjabi murmured (voiced aspirate) consonants have disappeared, and left tone in their wake. If the murmured consonant was at the beginning of a word, it left behind a low tone; if at the end, a high tone. If there was no such consonant, the pitch was unaffected; however, the unaffected words are limited in pitch so as not to interfere with the low and high tones, and so has become a tone of its own: mid tone. The historical connection is so regular that Panjabi is still written as if it had murmured consonants, and tone is not marked: the written consonants tell the reader which tone to use.
Similarly, final fricatives or other consonants may phonetically affect the pitch of preceding vowels, and if they then weaken to /h/ and finally disappear completely, the difference in pitch, now a true difference in tone, carries on in their stead. This was the case with the Chinese languages: Two of the three tones of Middle Chinese, the "rising" and "departing" tones, arose as the Old Chinese final consonants /ʔ/ and /s/ → /h/ disappeared, while syllables that ended with neither of these consonants were interpreted as carrying the third tone, "even". Most dialects descending from Middle Chinese were further affected by a tone split, where each tone divided in two depending on whether the initial consonant was voiced: Vowels following a voiced consonant (depressor consonant) acquired a lower tone as the voicing lost its distinctiveness.
The same changes affected many other languages in the same area, and at around the same time (AD 1000–1500). The tone split, for example, also occurred in Thai, Vietnamese, and the Lhasa dialect of Tibetan.
In general, voiced initial consonants lead to low tones, while vowels after aspirated consonants acquire a high tone. When final consonants are lost, a glottal stop tends to leave a preceding vowel with a high or rising tone (although glottalized vowels tend to be low tone, so if the glottal stop causes vowel glottalization, that will tend to leave behind a low vowel), whereas a final fricative tends to leave a preceding vowel with a low or falling tone. Vowel phonation also frequently develops into tone, as can be seen in the case of Burmese.
Tone arose in the Athabascan languages at least twice, in a patchwork of two systems. In some languages, such as Navajo, syllables with glottalized consonants (including glottal stops) in the syllable coda developed low tones, whereas in others, such as Slavey, they developed high tones, so that the two tonal systems are almost mirror images of each other. Syllables without glottalized codas developed the opposite tone—for example, high tone in Navajo and low tone in Slavey, due to contrast with the tone triggered by the glottalization. Other Athabascan languages, namely those in western Alaska (such as Koyukon) and the Pacific coast (such as Hupa), did not develop tone. Thus, the Proto-Athabascan word for "water" *tuː is toneless toː in Hupa, high-tone tó in Navajo, and low-tone tù in Slavey; while Proto-Athabascan *-ɢʊtʼ "knee" is toneless -ɢotʼ in Hupa, low-tone -ɡòd in Navajo, and high-tone -ɡóʔ in Slavey. Kingston (2005) provides a phonetic explanation for the opposite development of tone based on the two different ways of producing glottalized consonants with either (a) tense voice on the preceding vowel, which tends to produce a high F0, or (b) creaky voice, which tends to produce a low F0. Languages with "stiff" glottalized consonants and tense voice developed high tone on the preceding vowel and those with "slack" glottalized consonants with creaky voice developed low tone.
The Bantu languages also have "mirror" tone systems, where the languages in the northwest corner of the Bantu area have the opposite tones of other Bantu languages.
Three Algonquian languages developed tone independently of each other and of neighboring languages: Cheyenne, Arapaho, and Kickapoo. In Cheyenne, tone arose via vowel contraction; the long vowels of Proto-Algonquian contracted into high-pitched vowels in Cheyenne, while the short vowels became low-pitched. In Kickapoo, a vowel with a following [h] acquired a low tone, and this tone later extended to all vowels followed by a fricative.
In Mohawk, a glottal stop can disappear in a combination of morphemes, leaving behind a long falling tone. Note that this has the reverse effect of the postulated rising tone in Mandarin Chinese derived from a lost final glottal stop.
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