The subregular hypothesis posits that all phonological markedness constraints can be described by some principled, learnable subclass of the regular languages. In this article, I classify a wide range of attested long-distance phonological markedness constraints, covering stress, harmony and tone, with focus on interactions of constraints over multiple tiers. To this end, connections are established between propositional logic over multiple tiers and algebraic properties of formal languages. These techniques allow for mechanical verification or refutation of membership in a class. Modelling the constraints and their induced patterns as formal languages, I demonstrate that the entire range lies within the propositional level, including Uyghur backness harmony and Karanga Shona tone, which have been presented as challenges to aspects of the subregular hypothesis.
