This chapter examines a number of issues arising in multitiered nonlinear phonology in the light of the Obligatory Contour Principle (OCP), which prohibits adjacent identical elements at the melodic level. Multiple association of individual features or of a subset of a segment's features is found in processes of partial assimilation. The important point is that a spreading analysis of partial assimilation presupposes an articulated tier structure: In order for a certain feature of a given segment to be able to spread separately from all the other features contained in the segment, the spreading feature must be representationally autonomous. Taking the OCP as a guiding principle, we will argue that feature-sized cooccurrence restrictions can be understood as OCP-effects if the internal feature composition of segments is organized into a number of separate tiers. The OCP is the formal reflex of a general strategy to analyze identity of segments as multiple association of a single melodic complex and not as a melodic sequence of identicals.