Autosegmental phonology

Autosegmental phonology (the term is a blend of autonomous and segmental) was to represent tone (and most languages of the world are tone languages) apart from segments (morphemes) with which tone can be associated.

That was a challenge to the 'linear' approach which treats tones as part of the segmental features defining each segment. The idea is that tone is represented on a separate tier, and that words get their tones by association. There are rules of association: tones are associated to vowels one to one and left to right; if any vowels receive no tone by this procedure, the tone to their left spreads to them; if tones are left over after all the vowels are associated with tones, then the remaining tones attach to vowels already associated with tones, producing contour tones. For example, if there are five tones high, low Jailing, rising, rising-falling in a tone language, and these could appear on morphemes of one, two, or three syllables, then simple tones (high, low) are represented as a single specification, contour tones are a sequence of simple tones: falling is the sequence high-low; rising-fallingis the sequence low-high-low. Thus a falling tone may be divided among the two syllables of disyllabic forms but realized on the single vowel of a monosyllabic form.

Autosegmental formalism also helps to describe those cases in tone languages when a segment is deleted but the tone remains to be associated with another word.

This theory was extended to other features spreading over segments, vowel harmony, for example, in Turkish. The vowels of stems are fixed either as [+back] or [-back]. Then the feature spreads over to suffixes. Thus each word is associated to a single value of [+back], for instance.

In most recent versions of the theory all features are claimed to be autosegmental, but arranged according to a strict hierarchy. The feature hierarchy is an area of ongoing research. In the Russian language, for example, palatalization/velarization may be viewed as a case of a feature [+palatalization] spreading over two adjacent segments, a consonant and a vowel: [CV+palatalized]. The exact disposition of other prosodic features in the hierarchy of features is not resolved yet. For English two examples may be of interest: an affricate may be represented in terms of autosegmental phonology as two values, [—cont] and [+cont[ associated to a single timing slot; a long vowel may be associated with two timing slots.

Autosegmental phonology has not had much influence on English phonology, perhaps because English has neither tone nor vowel harmony. Nevertheless, it has been very influential in the recent development of phonological theory.

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