"Battle Symphony" (I believe it's official title is actually "Theme of Z.O.E,") "Innocent Love" & "Beautiful Disaster" are all tracks from the prequel OVA, "Zone of the Enders: Idolo" and they were featured on a promo CD that came with the Premium Package for the Japanese release of the first game. However, I'm not sure where "The Slayer Arrives" is from, I don't recall it playing in the game, was it featured in the OVA as well? If so I'm curious where it was taken from as it wasn't featured on the promo CD and no other soundtracks for the OVA exist, perhaps it was just recorded off the DVD?