Tone Contours

Contour tones have a moving pitch within a syllable — Mandarin Tone 2 (rising), Tone 3 (dipping), Tone 4 (falling), Cantonese low rising. Register tones are level — high, mid, low, with sharp transitions between syllables. African languages (Yoruba, Igbo, Zulu) typically use register tones; East Asian languages (Mandarin, Cantonese, Vietnamese) typically use contour tones. The distinction is not absolute — register systems show gliding allophones at boundaries, and contour systems decompose into level targets in some analyses (Pike, Tone Languages 1948). Nonetheless, the typological grouping holds.

John Goldsmith's 1976 MIT dissertation "Autosegmental Phonology" treated tones as a separate tier from segments, linked by association lines. Tones could spread (apply to multiple syllables), delete, dock, or float (exist without a host). The framework explained downstep (the lowering of subsequent tones after a low tone), tone sandhi (Mandarin's third-tone rule: T3 + T3 → T2 + T3), and floating tones in Bantu languages. Goldsmith's model became standard in tonal phonology and was extended to all suprasegmental phenomena. Larry Hyman's tonal typology work (1976 onward) built on this foundation.

Tone sandhi is the systematic alteration of tones in connected speech. Mandarin's most famous rule: when two third tones (low dipping) meet, the first becomes second tone (rising). "你好" (nǐ hǎo, "hello") is pronounced "ní hǎo." The rule applies recursively in longer sequences. Tianjin Mandarin has more complex sandhi affecting multiple tones. Min Chinese (Taiwanese) has elaborate sandhi where every non-final syllable changes tone according to position. Sandhi rules pose a learning puzzle — children must acquire underlying tones beneath surface alternations. Matthew Chen's Tone Sandhi (2000) is the comprehensive reference.

Mandarin-speaking children produce contrastive tones by 18-24 months — earlier than they produce contrastive segments in some cases. Patricia Kuhl's perceptual studies show infants discriminate tonal contrasts independently of linguistic experience until about ten months, when language-specific tuning narrows perception. Adults learning a tone language as L2 face severe perceptual difficulty — Anne Cutler and others have documented persistent tonal errors even in advanced learners. The acquisition asymmetry — easy for children, hard for adults — exemplifies critical-period effects in phonology.

All languages have intonation — pitch movement at the phrasal level conveying questions, focus, emotion. Tone languages superimpose lexical tones on intonational frames. Mandarin questions raise the overall pitch register but preserve relative tone shapes. Yoruba focus marking interacts with high-low tonal distinctions. Janet Pierrehumbert's autosegmental-metrical model (1980) and the ToBI transcription system extend to tone languages, though with language-specific elaborations. Mary Beckman, Sun-Ah Jun, and others have developed Mandarin ToBI (M-ToBI), Korean ToBI (K-ToBI), and similar systems.

Major tone families: Sinitic (Mandarin, Cantonese, Hokkien, Hakka — about 1.4 billion speakers); Tai-Kadai (Thai, Lao); Hmong-Mien; Vietnamese; Tibeto-Burman (Burmese, Tibetan); Niger-Congo (Yoruba, Igbo, Zulu, Shona — hundreds of millions across Sub-Saharan Africa); Khoisan; Athabaskan (Navajo, Apache); Otomanguean (Mazatec, Zapotec, Trique); Tlapanec; some Athabaskan; some Mesoamerican languages. Atypical cases: Swedish and Norwegian have a two-way pitch accent contrast; Punjabi has tonogenesis from voiced aspirated consonants. The geographic and genetic spread of tone is broader than commonly recognized.

Tonogenesis is the historical development of tone from non-tonal sources. The classic case is Vietnamese — six tones developed from the loss of final laryngeal consonants and voicing distinctions on initial consonants (André Haudricourt, 1954). Voiceless onsets generated high tones; voiced onsets generated low tones. Final glottal stops became checked tones; final fricatives became other tones. Similar processes operated in Chinese (the four tones of Middle Chinese descended from earlier tonogenesis), Punjabi (recently from voiced aspirated stops), and many languages. Tonogenesis is a productive area of historical phonology and demonstrates how phonemic systems re-organize.