A phonological rule proposed by Chomsky & Halle (1968) which assigns primary lexical stress to the antepenulimate syllable of words where the main stress rule has assigned primary stress to the final syllable. The final primary stress is reduced by the rule to a secondary stress. Thus the output of the main stress rule for baritone is bærɪˈtəʊn. The alternating stress rule converts this to ˈbærɪˌtəʊn
Chomsky N. & Halle M. (1968) The sound pattern of English. New York: Harper & Row.