In this paper it is argued, contra Chomsky (1995), that phonological factors like the prefer-ence for alternating syllable structures (or the avoidance of hiatuses and complex consonant clusters) and the striving for an alternating rhythm (or the avoidance of stress clashes and lapses) have the potential to (co-)determine morphological and syntactic structures wherever these are variable. Empirical support for this claim comes from analyses of corpus data from present-day and earlier forms of English and includes the presence or absence of the Middle English verbal ending -n, the variants of the indefinite article a/an preceding h-initial words, the distribution of the participial forms lit and lighted, and the restrictions bearing on attribu-tive constructions and sentence adverbs negated by not. Building on the tentative assump-tion that alternating patterns are universal tendencies conditioned by neurophysiological facts, an interactive activation model of language processing is sketched out and contrasted with a possible treatment of the variation phenomena in terms of Optimality Theory