Harry van der Hulst
The subject of this article is vowel harmony. In its prototypical form, this phenomenon involves agreement between all vowels in a word for some phonological property (such as palatality, labiality, height or tongue root position). This agreement is then evidenced by agreement patterns within morphemes and by alternations in vowels when morphemes are combined into complex words, thus creating allomorphic alternations. Agreement involves one or more harmonic features for which vowels form harmonic pairs, such that each vowel has a harmonic counterpart in the other set. I will focus on vowels that fail to alternate, that are thus neutral (either inherently or in a specific context), and that will be either opaque or transparent to the process. We will compare approaches that use underspecification of binary features and approaches that use unary features. For vowel harmony, vowels are either triggers or targets, and for each, specific conditions may apply. Vowel harmony can be bidirectional or unidirectional and can display either a root control pattern or a dominant/recessive pattern.