A portion of a SEGA interview with various members of the dev team...
SEGA: What’s with this FM Sound Unit toggle button for the SEGA Mark III Version of ‘Fantasy Zone’ !?
Yosuke Okunari: Well, I’m sure Horii-san is bursting to talk about it, so let’s just get started about the biggest bonus feature for Fantasy Zone, the FM Sound Unit!
Naoki Horii: We have a story behind this as well. When we decided to put the MK3 version of Fantasy Zone in as a bonus, there was this one guy at the office who said, “Only adding stereoscopic 3D? Pfft, boring!” Seriously, that’s what I deal with here! As I’ve said before, even just that takes a ton of time, but then they say that’s boring… You gotta wonder what the guys are thinking! (laughs)
The FM synthesis version of the Fantasy Zone music was actually used in a different game called Fantasy Zone: The Maze*. So, we lightly discussed with (Manabu) Namiki, who is in charge of the sound, if we could bring the music from that. But Namiki said “Wait just a minute!”
He interjected by saying “The music for Fantasy Zone and Fantasy Zone: The Maze has a different tempo, and even if we brought it over, there’s no way we could turn that into a palatable dish for people.” He also mentioned the songs for the boss battles didn’t exist as well.
*Fantasy Zone: The Maze is a dot-eating genre game released at the end of 1987. It’s known as Opa-Opa in Japan.
….But for some reason, we ended up thinking about how nice it would be to have a FM Sound version. I’m not exactly sure how we ended up there. (laughs)