Thanks Fredde and StreetTrash! I hope you like it!
We're talking about something that was broadcast over telecom with no interaction right? There was never a need for the voice acting to happen "exactly" at any time in relation to the game. So, if the music player takes a second to start playing, it should be fine.
The issue is not the initial sync, but the game's framerate. An error as low as 0.1 FPS causes a desync of about 5 seconds, which is way too much to be enjoyable.
Did you guys completely dub all the dialogue in the game?
Yes, except for the written dialog which was not dubbed in the original version to begin with, and an announcement at the end of the game to record the result password and send it to Nintendo for prizes.
Did you guys do sound effects that need to sync up with action on screen?
Yes, for example when the old man casts a spell. Even the music had to be synced to match in-game events.
It does make me wonder if it would be possible to create some kind of "subtitle" feature in a BS emulator, so you could play the game with the original japanese voices, with an english subtitle at the bottom.
Yes, but not with the original Japanese audio, since it's either lost or sealed in a Nintendo vault somewhere. The only version that survived is a VHS playthrough recording that got dumped on NicoNicoDouga, and it's polluted by in-game SFX. We were able to recover almost all of the music tracks because they were repeated several times during the playthrough, but subtracting SFX from a low-quality audio track hundreds of times is a whole different beast. Even then, I don't think it's a good idea in the first place unfortunately, since it would be very hard to play the game and read the subtitles simultaneously.