Threw together a quick analysis comparing the original game's soundtrack to this prototype demo's versions and pointing out what differs where. It was fun to do, even if in a much more rushed format than I have been doing my vids.
https://www.youtube.com/watch?v=bayTzfKKztAI includes a download link to a ZIP file of the songs so people can have them. Also shot that shit over to Mr.P's for archiving.
It super interesting going back and forth between the original music of the final release and this prototype stuff. They originally didn't have a unique track for Block 3-2 and just continued using Block 3-1's music, but then you hear what ends up being the "Waterfalls" track in Stage 5. They must have just been shifting things around as Adachi and Taro made more music. Makes me wonder why they didn't bother keeping the prototype's Stage 2 music and just putting it in Block 2-2 instead of nixing it altogether for "Forest of Monsters" in the final release.