Vowel harmony in classical Generative Phonology

This chapter reviews publications in the early generative literature that addressed the challenges vowel harmony poses for a model of phonology whose archetypical rule changes the feature coefficient(s) of a single segment based on local context. These challenges include the Multiple-Application Problem (how to extend the feature change to multiple points in a harmonic span), the Directionality Problem (how to express progressive, regressive, and bidirectional assimilation as parameters of variation), the Duplication Problem (whether and, if so, how the same feature co-occurrence restriction can be stated over static roots and alternating affixes). Additional problems concern whether attested harmonic changes can be accommodated to a representational system based on distinctive features with consistent phonological and phonetic correlates (the Diacritic Problem) and whether both values of a feature assimilate (the Binarity Problem).