I know you can rip songs from ps2 discs, but is it possible to reverse the process and add songs, like off of spork's site, to a ripped game and burn it as an .iso for play on ps2
Guitar Hero is setup differently than IIDX is. I don't know if that's possible because even if you did add songs, you'd have to back convert them so the game will see them and even then, it might have some sort of preset cache file that has the songlist it's supposed to have so if you add other songs, it may not see them or freeze when you try to play them.