For those wanting to get straight to the business, the track-listing is available below via Archive.org.

For those still with us, please let me explain how I came to retrieve these soundtrack files for this mostly forgotten game from the guys who brought you classics such as Theme Hospital and Theme Park.

Theme Aquarium (later simply Aquarium once ported to Microsoft Windows) is a simulation video game in which you create and control a sea life aquarium – similar in tone to the later Zoo Tycoon: Marine Mania title. Originally released for the Sony Playstation in Japan only (テーマ アクアリウム), the game was later ported to Microsoft Windows and renamed to just Aquarium. I came across this title at a boot fair and I have a thing for old “tycoon” style games, and was bemused by this title’s existence.

Unfortunately the game doesn’t run under Windows 10 (or any modern Windows operating system for that matter), and I am yet to organize myself to play this on traditional of the time hardware. So in the meantime I have, like always, taken a digital copy of the files (as more of a “just in case” and for convenience) and as I can’t play the game yet started poking around the files that are there.

Being the uber nerd I am I like to try and decode what files I can in the program files, just to see how they are made or encoded and what the possiblities might be to amend them (usually for comedic effect) or to uncover hidden items, hoping one day to have something worthy of a Did You Know Gaming episode.

The type of files I often like to try and extract are audio files. This covers both music files (for things like background music) and sound effect/speech files. The former I try and make available online as there is often a hidden beauty to a lot of video game soundtrack music, and the latter I usually keep for the day I finally get round to making music. Either way, its an interesting excerise to perform.

So in the case of Aquarium the soundtrack files are all kept under the directory path \Game\Sound and are all marked as .SDF files. When searching online for what an SDF file might be (using my recommended repository, FileInfo.com) there were no useful results. The most common file type that carries that extension is the SQL Server Compact Database File, which this certainly is not. The other results that are reported on the FileInfo page also do not match, and none of them are of a multimedia kind. So I took the original .SDF files and uploaded them to VirusTotal. Don’t worry I don’t think that these simple audio files would be malicious, but I like to see what the VirusTotal analysis machine can return about these kind of files while also creating a signature file for them and confirming them to be clean for the community.

Upon uploading the first file (bgm01.sdf) the following information was uncovered about the files; they were RIFF WAVE files using Little Endian encoding, 16-bit depth with a sample rate of 11025Hz. Excellent so these are effectively just .WAV files that have been renamed to obscure them from the system. Luckily for everyone these files feature a properly formed header and so you can simply rename them to .WAV (i.e. bgm01.wav) and they will playback correctly in any decent multimedia player (my preference being VideoLAN’s VLC Player).

I have converted them from .WAV to .MP3 files which allows them to be easily embedded and played back in a web browser, and compatible with probably 90% of audio players that exist. Unforunately because the game doesn’t use CD-ROM audio (the technology of having the audio tracks as Red Book audio tracks on the media), the files are compressed as to not take up too much space on the hard drives of the era. For that reason the 11025Hz bitrate has reduced the fidelity of the audio.

As I haven’t played the video game yet, I haven’t been able to give any of the tracks interesting names so they all carry their filenames as their titles. Almost all of the tracks are 3 minutes long and have a uniquely 90s “underwater” feel to them. BGM09 appears to be a success sound (4 seconds in length) and BGM10 appears to be a failure (game over) sound (5 seconds in length). BGM27 is the only other item that isn’t 3 minutes, instead 9 seconds, but it is unclear when it would trigger in the game.

Another item of extraneous information, there are 8 movie files (\Game\Movie) which are .MDF files, these are actually just MPEG Layer 1 clips and much like the audio files simply require an extension rename to .MPEG and they will then playback.

Well hopefully this was an interesting read for you. If you have a video game which features .SDF files then I hope this post will help you figure out how to play (and later convert) them.