Rhythmic syncope describes the deletion of vowels in an alternating rhythmic pattern, so that every other underlying vowel deletes. We informally summarize a proof that rhythmic syncope cannot be represented by a strictly local function over segments. Rather, rhythmic syncope can only be generated by a strictly local function if input and output symbols are synchronized, so that locality can be computed over both the input and output value at a particular time step. This structural property may only be needed to describe rhythmic syncope, which means that before concluding that human phonology can compute such functions, it is essential to verify the extent to which rhythmic syncope is attested as a stable and productive synchronic pattern.