The factors that enter into the production and perception of rhythm in singing are so varied and complex that they almost defy clarification. In discussing rhythm of the singer, musicians have confined themselves almost entirely to one general term: stress, with its loose synonyms, accent and emphasis. These terms are not well-defined, although generally the context implies that stress, accent, and emphasis mean an increase in dynamics, a push in intensity. It is the purpose of this paper to attempt to clarify the nature of vocal rhythm by discussing some studies of two major factors that are involved: time stress and intensity stress