Quote Originally Posted by Kawaii Ryűkishi
Yeah, it's usually not called "Prologue" since it tends to be spliced into some other track, like the staff roll. And it was absent from FFX as well as FFII.
I'm not 100% sure what song you're talking about since I can't get that video to work for some stupid reason, but I would assume you're thinking of that one that tends to start off with a long harp intro, right? Well, it was in Final Fantasy X, in the part where Tidus is signing Blitzballs at the beginning. It's called The Prelude. I can link you to the song, if it's not against the rules here.