When a medial consonant cluster is simplified by deletion or place assimilation, the first consonant is affected, but never the second one: /patka/ becomes [paka] and not *[pata]; /panpa/ becomes [pampa] and not [panta]. This article accounts for that observation within a derivational version of Optimality Theory called Harmonic Serialism. In Harmonic Serialism, the final output is reached by a series of derivational steps that gradually improve harmony. If there is no gradual, harmonically improving path from a given underlying representation to a given surface representation, this mapping is impossible in Harmonic Serialism, even if it would be allowed in classic Optimality Theory. In cluster simplification, deletion or Place assimilation...