I've fiddled with this a bit and haven't been able to figure it out, but I'm not a technical wizard in the least! I'd also be interested in knowing.
I also would like to know if there's a way to replace an ogg file for episode 4 music without having it bug out. What happens when I try is that no music will play, then the game will freeze/crash when you try returning to Pioneer.
I guess you refer to the "multi stream" oggs, they are used only in specific areas (not all OGGs can be made that way, for PSO), and there isn't any tag for that.
You have to divide your ogg in very small sound chunks which pso plays based on certain variables.
That's why if you grab a "normal" song and put it into these oggs, they "bug" out.