INTERPLAY • DICTIONARY ONE.COM • Definition of Interplay

... usual, namely, that of either pitch or stress for duration. In other words, the groups that make up a rhythmic series may be determined or marked off by emphasis of pitch or emphasis of stress as well as by duration of time. In fact, it is from this habitual interplay of the three elements that most of the complexity of metre arises; as it is the failure to recognize this substitution which has given the older prosodies much of their false simplicity and ...

— The Principles of English Versification • Paull Franklin Baum