Phonetic Similarity in Tonemic Analysis with Notes on the Tone System of Akwapim Twi

Abstract

The analysis of tone phonemes, or tonemes, like that of segmental phonemes, necessarily involves considerations of phonetic similarity-necessarily, because there is no other basis upon which tones occurring in noncontrastive distribution can be phonemically identified with one another. But how is 'phonetic similarity' to be understood in the case of tones? Not, certainly, in the sense in which it is understood in the case of segmental phones, where it denotes some objective similarity in the articulatory or acoustic characteristics of the phones themselves. To be sure, even in this case phonetic similarity is a rather elastic criterion; but at least it can be shown, for example, that two vocalic phones have a common tongue position, or two consonantal phones certain common distinctive features. No such objective similarity is demonstrable in the case of tones-at least, of level tones; for, since it is relative rather than absolute pitch that is involved in tonemic systems, a given toneme may occur at virtually any pitch of which the voice is capable. Variants of a man's high tonemes may be acoustically similar to those of a woman's low tonemes; and in the speech of a single speaker a given level of pitch in two utterances or even within one utterance may represent variants of several different tonemes. The possibilities of phonemic overlapping of level tonemes are virtually unlimited. That there is no necessary objective similarity between the pitch levels of tonemic variants does not mean, however, that there is no objective basis for considering the variants phonetically similar. It means only that the basis must be something other than the intrinsic properties of the variants themselves. What other basis is there for considering tones in noncontrastive distribution phonetically similar, and hence variants of a single toneme? The answer that suggests itself is, a similar distinctive relation of the tones to their respective environments. In other words, however acoustically diverse the variants of a given toneme, and however much they overlap those of other tonemes, they may still have in common a relation to their respective phonemic contexts unique to the toneme of which they are members. Such a distinctive relation to the context-and such a relation alone-satisfies the criterion of phonetic similarity in the case of tones. To offer a hypothetical case. In language A, which has a level-tone system, two contrastive tones-one relatively high, the other relatively low-occur with each vowel. The higher tone that occurs with certain vowels is acoustically similar to the lower tone that occurs with certain others. This fact, however, is irrelevant to the phonemic identification of the tones. For, since the basis of this identification is the relation of the tones to their context, rather than the acoustic character of the tones themselves, the CONTRASTIVELY higher tones (whatever their actual pitch) are identified as variants of one toneme, the CONTRASTIVELY