The balanced rythmic flow of poetry or oratory is referred to as cadence.
Cadence is the rise and fall of the voice that creates a melodic pattern when reading, or even when talking in general. Some languages have a cadence that is more pronounced than others, such as Italian.
A change in cadence can also influence the meaning of a sentence or word. For example, saying "He is a great person" can mean very different things depending on where the emphasis of the intonation is. If the cadence emphasizes "great" instead of "person", the sentence could have a sarcastic meaning.