Tone letters are letters that represent the tones of a language, most commonly in languages with contour tones. They are used both in language orthographies, such as Hmong, and phonetic transcription, such as the IPA.
Chao tone letters (IPA)
A series of iconic tone letters based on a musical staff was devised by Yuen Ren Chao in the 1920s by adding a reference stave to the existing convention of the International Phonetic Alphabet. The stave was adopted by the IPA as an option in 1989 and is now nearly universal. When the contours had been drawn without a staff, it was difficult to discern subtle distinction in pitch. Only nine or so of the possible tones were commonly distinguished: high, medium and low level, [ˉa ˗a ˍa] (or as dots rather than macrons for 'unaccented' tones); high rising and falling, [ˊa ˋa]; low rising and falling, [ˏa ˎa]; and peaking and dipping, [ˆa ˇa], though more precise notation was found and the IPA specifically provided for mid rising and falling tones if needed. The Chao tone letters were originally x-height, but are now taller to make distinctions in pitch more visible. Combinations of the Chao tone letters form schematics of the pitch contour of a tone, mapping the pitch in the letter space and ending in a vertical bar. For example, [ma˨˩˦] represents the mid-dipping pitch contour of the Chinese word for horse, 馬／马 mǎ. Single tone letters differentiate up to five pitch levels: ˥ 'extra high' or 'top', ˦ 'high', ˧ 'mid', ˨ 'low', and ˩ 'extra low' or 'bottom'. No language is known to depend on more than five levels of pitch. These letters are most commonly written at the end of a syllable. For example, Standard Mandarin has the following four tones in syllables spoken in isolation:
For languages that have simple register tones in basic morphemes, or on short vowels, single tone letters are used for these, and the tone letters combine as the tones themselves do to form contours. For example, Yoruba has the three basic tones [˥ ˧ ˩] on short vowels and the six derived contour tones [˥˧ ˥˩ ˧˥ ˧˩ ˩˧ ˩˥] on long vowels, diphthongs and contractions. For languages that have basic contour tones, among these are level tones, and it is a common convention to use double tone letters for those level tones while using single tone letters for short checked tones, as in Taiwanese Hokkien [sã˥˥] vs [tit˥]. The tones [˥˥] and [˥] are generally analyzed as being the same phoneme, and the distinction reflects traditional Chinese classification; it also derives from the convention of numerically writing ⟨sã55⟩ for high level pitch vs ⟨sã5⟩ for tone #5. Regardless, this is not an IPA convention. Chao tone letters are sometimes written before the syllable, in accordance with writing stress and downstep before the syllable, and as had been done with the unstaffed letters in the IPA before 1989. For example, the following passage transcribes the prosody of European Portuguese using tone letters alongside stress, upstep, and downstep in the same position before the syllable:
[u ꜛˈvẽtu ˈnɔɾtɯ kumɯˈso ɐ suˈpɾaɾ kõ ˈmũitɐ ˩˧fuɾiɐ | mɐʃ ꜛˈku̯ɐ̃tu maiʃ su˩˧pɾavɐ | maiz ꜛu viɐꜜˈʒɐ̃tɯ si ɐkõʃꜜˈɡava suɐ ˧˩kapɐ | ɐˈtɛ ꜛkiu ˈvẽtu ˈnɔɾtɯ ˧˩d̥z̥ʃtiu ǁ] O vento norte começou a soprar com muita fúria, mas quanto mais soprava, mais o viajante se aconchegava à sua capa, até que o vento norte desistiu. The two systems may be combined, with prosodic pitch written before a word or syllable and lexical tone after a word or syllable, since in the Sinological tradition the tone letters following a syllable are always purely lexical and disregard prosody. Diacritics may also be used to transcribe tone in the IPA. For example, tone 3 in Mandarin is a low tone between other syllables, and can be represented as such phonemically. The four Mandarin tones can therefore be transcribed /má, mǎ, mà, mâ/. (These diacritics conflict with the conventions of Pinyin, which uses the pre-Kiel IPA diacritic conventions: ⟨mā, má, mǎ, mà⟩, respectively.) There is not a one-to-one correspondence between Chao tone letters and the IPA tone diacritics, despite the simplistic presentation on the IPA chart. Two examples are given in the Report of the 1989 Kiel Convention, for languages with three and four register tones:
As shown, the acute accent corresponds to the highest Chao tone letter in a 3-tone system, but to the 2nd-highest in a 4-tone system. However, even this is not absolute. For example, a four-tone language might be analyzed as having high, mid, low and extra-low tones, /x́ x̄ x̀ x̏/, or some other arrangement, but the tone letters could still reflect acoustic pitch independently of that analysis.
Reversed Chao tone letters Reversed Chao tone letters indicate tone sandhi, with the right-stem letters on the left for the underlying tone, and left-stem ('reversed') letters on the right for the surface tone. For example, the Mandarin phrase nǐ /ni˨˩˦/ + hǎo /xaʊ˨˩˦/ > ní hǎo /ni˧˥xaʊ˨˩˦/ is transcribed:
⫽ni˨˩˦꜔꜒xaʊ˨˩˦⫽ Some transcribers use reversed tone letters to show that they apply to the following rather than the preceding syllable. For example, Kyoto Japanese ame 'rain' may be transcribed,
꜖a꜒꜔me rather than a˩me˥˧. Reversed tone letters were adopted by the IPA in 1989, though they do not appear in the space-limited IPA chart. The phonetic realization of neutral tones are sometimes indicated by replacing the horizontal stroke with a dot: ⟨꜌ ꜋ ꜊ ꜉ ꜈⟩. When combined with tone sandhi, the same letters may have the stem on the left: ⟨꜑ ꜐ ꜏ ꜎ ꜍⟩. This is an extension of the pre-Kiel IPA convention of a dot placed at various heights to indicate the pitch of a reduced tone. Chao defined the pitch trace as indicating a 'toneme' when to the left of the stave, and as a 'tone value' when to the right. However, 'tone value' is not precisely defined, and in his examples may be phonemic. His illustrations use left- and right-facing tone letters as follows:
English jes꜓꜕, jes꜒꜖, jes꜕꜓, ɦjes꜖ etc: different intonations of the response 'yes' Cantonese i˩kɑ˦˨꜒: a phonemic change in tone due to sandhi in a compound word Lhasa Tibetan lɑ kɑ˩˧˩wɛ > lɑ꜖ kɑ꜔꜒wɛ꜕: the spread of an underlying peaking tone on kɑ across adjacent syllables The Tibetan distinction is a phonemic-phonetic one; the Cantonese distinction is not.
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