Subnautica-like BGM Generator -- RPG Maker MZ

FATHOM forges original ambient underwater music — evolving pads, deep drones, a lonely piano and plaintive winds — that drift and breathe, from scratch in your browser.

This is atmosphere over melody. Instead of a beat-driven tune, FATHOM slowly drifts through sustained sonorities over a continuous drone, with sparse reflective piano, bowed cello and solo wind floating through sonar pings, bubbles and whale-song — all wrapped in a vast underwater reverb that gets more muffled the deeper you go. It's a dev tool: make a drift, export it, drop it into your game.

What makes it different

• Truly ambient, not a sequencer. No strict beat grid — it's time-and-texture based: evolving pads, long reverb tails, and lots of space, exactly where survival/exploration games live.
• Depth changes everything. One master dial darkens the harmony, lowers the register, adds dissonance, and literally muffles the whole mix as you descend from sunlit shallows to the crushing abyss.
• Twelve biomes, twelve atmospheres:
  • Shallows — warm wonder, soft piano & bells
  • Kelp — flowing green calm
  • Reef — vast awe, whale calls
  • Grotto — enclosed mystery, piano & drips
  • River — eerie cold, glassy shimmer & choir
  • Abyss — dark foreboding, sub-bass & cello
  • Magma — molten weight, deep and slow
  • Leviathan — dissonant terror, stingers & heartbeat
  • Surface — bright open relief
  • Wreck — industrial unease, metallic clanks
  • Precursor — alien sanctum, quartal glass & choir
  • Solitude — the lonely reflective piano moment
• A from-scratch ambient palette: warm/glass/dark evolving pads, sub-bass drone, felt piano, plaintive wind, bowed cello, bells, glass harmonica, wordless choir — plus textures: sonar, bubbles, low rumble, tension swells, creature stingers, industrial clanks and whale-song.

You're in control

• Depth — sunlit, bright and consonant → abyssal, dark, muffled and dissonant.
• Current — from still and meditative to turbulent and active.
• Tension — from serene to harrowing (unease, dissonant swells, creature stingers).
• Plus Key, Length, and a Pulse mode: Drift (pure ambient), Tide (slow breathing swells), or Sonar (periodic pings).
• New drift rolls a fresh seed — new mode, key, harmonic drift, lead instrument and palette every time. The seed + sliders reproduce any drift exactly.

Export & drop in

• .ogg — game-ready, with LOOPSTART / LOOPLENGTH loop tags baked in. Drop it into audio/bgm/ and RPG Maker (MZ and MV) loops it seamlessly. (Ambient loops are long and reverb-heavy — seamless looping matters, and it's built in.)
• .wav — uncompressed, for editing in a DAW.

Good to know

Runs offline in any modern browser — nothing installs, nothing uploads. A short README with full instructions is included.

FATHOM emulates the style and techniques of ambient underwater game scores; it does not contain or reproduce any existing music, and is not affiliated with or endorsed by Unknown Worlds, Subnautica, or any other rights holder.

FAQ

Is the music royalty-free? Can I use it commercially? Yes. Everything FATHOM exports is original and yours to use in commercial or free projects, no attribution required. A credit ("Music forged with FATHOM") is appreciated but optional.

Does it use samples or copyrighted audio? No. Every sound is synthesized from scratch with the Web Audio API. It never reproduces any existing track — it emulates a style.

Will the loops loop seamlessly in RPG Maker? Yes — export the .ogg. It carries LOOPSTART/LOOPLENGTH tags MZ and MV read to loop with no gap, which matters a lot for long ambient beds. (The .wav has no loop tags; use it only for DAW editing.)

MZ only, or MV too? Both. They both read .ogg for BGM. Put the file in audio/bgm/.

Can I use these outside RPG Maker — for a Unity/Godot game, video, or stream? Yes. The .ogg/.wav are ordinary audio files you can use anywhere; the loop tags are simply ignored by tools that don't read them.

Do I need to install anything or be online? No. It's one .html file — download it, open it in a browser, work offline.

How do I get the exact same drift back later? Note the seed on screen and keep your slider + Pulse values; re-enter them for an identical render.

No sound when I open it? Click Play once. Browsers block audio until you interact with the page.

The OGG button says the encoder didn't load. Refresh and retry. Fallback: export the .wav and run ffmpeg -i track.wav -c:a libvorbis track.ogg (no loop tags that way; prefer the built-in OGG export).

Is this "AI music"? The composition and sound come from hand-written procedural DSP code — not a generative-audio AI model. The tool's code was developed with LLM assistance, which is disclosed above.

Feedback, Support & Custom Development

Thank you for checking out this project! If you use this plugin, I'd greatly appreciate it if you could leave a review describing your experience. Your feedback helps improve future updates, assists other developers in making informed decisions, and supports continued development.

If you have any questions, bug reports, feature suggestions, or run into any problems while using this plugin, please don't hesitate to contact me.

I'm also available for custom RPG Maker plugin development. Whether you need a completely new plugin, modifications to an existing one, compatibility fixes, or help implementing a unique gameplay system, I'd be happy to discuss your project.

📧 Contact: rpgmakerplugins@protonmail.com

I do my best to respond as quickly as possible and look forward to helping you bring your ideas to life. Thank you for your support!