One of my teachers in graduate school used to say the difference in repetition and reiteration is that repetition diminishes meaning while reiteration increases meaning.
The repetition in musical Minimalism (think Reich's Come Out or Glass's Einstein on the Beach) is my go-to example for evaluating meaning, or the change in meaning, in repetition. In my own experience, my perception changes gradually over time even when listening to this kind of music. First, I sense the repetition on a local level ("Oh, this isn't going to change, huh?"). Second, I become annoyed and impatient (this happens less now than it used to). Third, I give in and slip into a different mode of perception (some people think of this as a trance; it comes with practice)--a mode that allows me to connects dots that are farther apart, so to speak. The big picture comes into focus and time becomes less important--like I'm looking at a picture, with the freedom to direct my intentionality around a space rather than being locked in the moment, as in traditional goal-oriented music.
I heard a Radiolab episode recently called Loops that dealt with a couple of things that reminded me of musical Minimalism and raised a couple questions about the meaning of repetition. One of the vignettes deals with the composer William Basinski's Disintegration Loops, a series of recordings of old, decayed analog tape loops repeating until they literally disintegrate. This certainly follows one common model of Minimalism: A gradually transforms into B. In addition to the listener's perception changing over time, the music changes literally, though almost imperceptibly.
Kristen Schaal Is a Horse, which is dealt with the episode's first vignetter, on the other hand doesn't change. It is literally AAAAAA.... It's a comedy (or anti-comedy) bit she does with Kurt Braunohler (there's a video below, check it out). But unlike the musical Minimalists, Schaal and Braunohler don't change gradually (except as a result of the physical demands of the performance--hoarse voice (no pun), for example). They seem to undermine even the assumption that something must change, progress, evolve, etc. In the world of comedy this is an extreme version of jokes that run absurdly long on purpose (the giant chicken on Family Guy, for example). My perception of these too-long jokes is analogous to my perception of musical Minimalism (i.e. become aware of the repetition, become frustrated that it's going on too long, then give in), except in this case giving in means to laugh. The transparent, literal repetition in the Schaal/Braunohler gives us a good way to control for the change in perception that occurs (if any). My perception does change; in fact it does all the work. At the end* Kristin Schaal may still be a horse, but the viewer has just experienced a surprisingly rich perceptual journey precisely because nothing happened.
*I understand they have done this bit for up to 10 minutes or more in some performances (or maybe it just felt that way to some people--I haven't seen a longer video).