These root stresses are in many ways the anchor around which alliterative meter is organized. In practice, this means that we have to pay attention to the parts of speech. The grammatically important words are the content words. Finally, the actual rhythm is important. Words and syllables fall naturally into rhythms in which some elements are stronger, or more prominent, than others.
Poetry organizes the rhythms, but the rhythms themselves are based on the natural flow of speech.
At the lowest level, we can observe a rise and fall of accent every few syllables, and we can group the syllables based on that alternation. But the organization of rhythm doesn't end there. All of the syllables in a sentence tend to group into small phrases, about the length of a long word. Some of them are words, others are a cluster of words that can be pronounced together as if they were a single word. Linguists term these prosodic words .