From what I can find, it’s actually the demo Christmas NiGHTS into Dreams… that did that. The full game also uses the system time for changes but not that specifically-

The A-Life system features an evolving music engine, allowing tempo, pitch, and melody to alter depending on the state of Nightopians within the level. The feature runs from the Sega Saturn’s internal clock, which alters features in the A-Life system depending on the time.

EDIT: Not particularly exciting, but I found and took a picture of my copies - evidently the Christmas demo came from Blockbuster Video.

It’s not web based but MKVToolNix GUI is pretty user friendly. I haven’t dug into it too deeply so I don’t know if it offers any automation tools to batch change files etc.

I whipped up a basic page with PHP and just used XAMPP when I was on Windows. I recently switched my daily driver pc to linux and haven’t updated it yet. I only used it to save MP3s, videos at yt-dlp default “best available” settings, and a custom option that lists available video/audio formats where I can specify the ID to grab of each. No validation or sanity checking etc, just some switch statements and basic form functions.

main page

custom selection