It has been observed that in languages with dominant-recessive harmony
systems, while either roots or suffixes can be dominant (i.e., they can
trigger a phonological change in their surrounding elements), prefixes are
always recessive (Clements 2000, Bakovi´c 2000, Casali 2003 a.o.). While
the ‘no dominant prefixes’ generalization is acknowledged in most studies
of dominant harmony systems, there is, to our knowledge, no systematic
explanation for the pattern. We propose that the generalization is
epiphenomenal, a special case (when it holds) of a broader generalization
that phonological derivations of morphologically complex words proceed in
stages, which may correspond to syntactic phases. Specifically, following
Newell 2008, Fenger 2020 a.o., we propose that elements in the first domain
may have unrestricted phonological interactions, including
structure-changing operations, but that beyond the first phase/domain,
phonological operations may not change material that is fixed on the first
cycle. For vowel harmony, this predicts that ‘low’ affixes may be dominant
(root-altering) or recessive, but that ‘high’ affixes that participate in
vowel harmony (contra Fábregas & Krämer 2020) may only be recessive. Since
it is independently established that prefixes tend to represent
syntactically higher morphemes than suffixes (Julien 2002), ‘no dominant
prefixes’ as a trend falls out as a special case.