I once heard a porcupine being attacked by what I think was a fisher. The noise sounded something like your recording, although with more of a tone of anger and distress mixed in.
It’s possible that you were hearing something of the sort. (The squeal at 3:00 and forward and especially at about the 4:00 mark, sounds frightened.)
We do have fishers in the area, so that is a possibility.
But if two animals were fighting, I would expect more movement in the treetops. I saw none. Also, if a predator was attacking another animal, he would get it over pretty quickly. Three hours is a lot to wait to eat your dinner after the appetizer. A baby missing its mom is more likely.
According to Wikipedia, fishers attack porcupines by repeatedly biting them on the face over a period of 20 to 25 minutes, presumably until the poor porkie weakens from loss of blood. Now that’s not 3 hours, but some of the time might have been preamble before the attack started in earnest, and maybe it was a young, inexperienced fisher or a large, robust porcupine.
Not saying that’s definitely it, but what I heard at the 3-4 minute mark in your recording sure sounded like the attack I heard years ago.