ATR vowel harmony in Ateso

Vowels in Ateso, an Eastern Nilotic language, are subject to Advanced Tongue Root (ATR) harmony. Accordingly, the vowels are divided into two harmony sets which differ in terms of tongue root position. The two sets of tongue root position are the Advanced Tongue Root [+ATR] set and the Retracted Tongue Root [-ATR] set. Comparably, Bari and Lutuko, related Eastern Nilotic languages, have a ten-vowel system consisting of five closed and five open vowels, with clearly discernible laws of ATR vowel harmony (Tucker & Bryan 1966ː 444). A similar system applies to Ateso which has the following nine phonemic vowels: /i ɪ e ɛ u ʊ o ɔ a/ and the phonetic vowel [ä]. The presence of the [ä] variant is conditioned by neighbouring [+ATR] vowels or glides, and hence does not have phonemic status; instead, it is treated as an allophone of /a/. In this paper, I follow the general discussion of vowel harmony in African languages (e.g. by Casali (2003, 2008)), albeit in Ateso. Firstly, I introduce the Ateso vowel articulatory parameters and the phonetic realisation of /a/. Secondly, I show that in Ateso /a/ behaves like an underlying [-ATR] vowel and that, generally, though the ATR affects tongue height and thereby accounts for the relative tongue height, ATR is not a category of tongue height but rather of the position of the tongue root. Lastly, I demonstrate that Ateso ATR vowel harmony has two dimensions. One is the condition that vowels ideally belong to a [-ATR] or [+ATR] set within a word and the second is that there is a dynamic dimension where ATR qualities may change as a result of affixation.