I have been working on a VN for Saturn myself... I am puzzled on how to add the sound though, which I see you were able to do in RM. Would you be willing to share a snippet of the code to add the audio to get me started?
Here is the source code of my last visual novel for th saturn, The Case of the City Botucaiba (https://neuromage.itch.io/botucaiba). The game features music and visual novel dialog navigation.
https://github.com/GSansigolo/The-Case-of-the-City-Botucaiba