From the National Book Foundation interview with Keith Waldrop:

CMT: This is an unusual book—really three books in one, which you call a trilogy. Can you explain how you wrote them?

KW: It came about for a very specific reason. The problem was that I had to become the director of a program at Brown.... It was not a difficult job, but it was endless. I kept thinking after hours about what I should do tomorrow and what I didn’t do yesterday, and I found after some months that I was not writing any poetry, and I didn’t like that, so I decided midnight would be the hour when Brown would disappear for me and I’d work on my poems no matter what. I decided to do some collage work with my poems, and the mechanical part of it, just getting words from somewhere, I thought would be something I could do without thinking, so I got a batch of books and put them on the table—the plan was very simple, I put three books in front of me, all prose, a novel, then something psychological, then whatever I happened to have around. I would take phrases from these three books and make some stanzas, four, five six lines. Once I had that I’d make more stanzas of the same number of lines, and when that gave out, after a page or two, I’d say alright I have this poem now and I would take it to the typewriter and type it up and in doing so I would rearrange the stanzas alphabetically. I wasn’t worried about keeping the words exactly what they were—sometimes I changed words. I wasn’t trying to prove anything about collage, I was trying to write poems. Then I would put a title on it and put it aside. Then after a matter of weeks, I had something book length, when it wasn’t working anymore, I stopped. At that point I rearranged all the poems by title and that was the second part of the book. The first and third parts are mainly collage, a little less. I had different ways of working with it.

And from an interview with poet, Peter Gizzi, at Siglio Press:

PG: Would you say that this idea of revision or collage is an act of recuperation, a restructuring or rearranging of what would be linear time?

KW: I've sometimes been irritated by people "reading" my collages. "This looks like. . ." is not objectionable, but "This means . . ." makes little sense to me. It's hard to carry this across verbatim into the verbal collages, since I would hardly want to say, "Don't read my poems, just look at them." But something maybe like "Read what it says, not what it means" might be an analog. Or better: Vygotsky distinguished between 'meaning' and 'sense': the 'sense' of a word or text being everything a word or text does, all its effect whether intellectual or emotional or whatever. 'Meaning' being the central, more or less definite content -- what, in some cases, you'd go to a dictionary for. So that meaning is a part of sense, but only a part. Vygotsky says that our "inner speech" emphasizes sense at the expense of meaning. I once applied that idea to Gertrude Stein's writing, but I think it's a useful notion for art in general. A translation, for instance, that brings across only the meaning of a poem or novel is not adequate, is only a start. And to explicate or "figure out" a poem, without really listening to it, is to avoid the poem, to short-circuit it.

To get back to your question, collage is certainly rearranging things. And often, in my case, using elements that might otherwise be thrown away. Old posters or. . . whatever. Or memories that could be thrown away. What do you do with memories, that in many cases hardly seem worth writing down. But as an element of collage . . .