When one re-remembers a memorized poem, one does not have to have the entire poem in mind at a single instant of time. Rather, the poem unfolds through time, just as it does when reading from a page. One is in a sense "reading" the poem from the memory. For example, I might not know the couplet of a Shakespearian sonnet until I get there. (Give me the first line of the sonnet and I can give you the second line, but to give you the concluding couplet, I would have to go through the entire thing in my head until I got there.) Memorization involves a complex relationship to ongoing duration. If you're interested in that kind of thing.

In fact, the human experience of the "present" always involves "just having been there" and "where I am about to be" as well as "where I am now." The present is the cusp; it hardly exists except as a sense of time passing, of duration and ongoing measure. Rhythm only works in time. It cannot function as a series of isolate flecks. I don't want to fetishize memorization, because I have to respect that fact that some people simply aren't memorizers. They simply don't relate to poetry in that way, and I'm not about to criticize them for that, much as I fail to understand them.