I can't tell if this is a jab at our conversation in the Syria thread, or just an honest misspell... It can work either way.
It's an auditory illusion created through the use of a sort of 'super-position.' By playing several tones at different octaves, it becomes impossible to tell where your note actually ends and begins. By phasing in at the high/low spectrum (depending upon whether you want to generate a 'rising' or 'falling' illusion), respectively, you can create the illusion that a note is endlessly falling/rising.
The ones that tend to mess with people are those that play around with superharmonics and binaural beats. Particularly with limited bit-depth audio, the use of superharmonics uses very high pitched frequencies that tend to affect teenagers more than adults. While these frequencies combine with lower-pitched tones to create effects older people still perceive - the higher notes are heard directly by younger people and it tends to be irritating.
Binaural beats tend to induce headaches and even mild paranoia. The idea is that you have a music track that plays at slightly different tempos through each speaker (or certain tones do - depending upon what you're trying to do).
A notable example of this is the notorious "Lavender Town Tone" - back when game developers were experimenting with techniques like that, the original Red and Green version of Pokémon contained the sound-track for Lavender Town that was supposed to give a very unearthly and creepy sensation. There are plenty of desynched tones and superharmonics there that succeeded in the goal of creeping people out.
So they stripped it from later production runs (the U.S. versions). Contrary to what you'll find on some of the internet - there were no suicides determined to be related to listening to the tone (though it makes for a good, creepypasta). Likewise, the frequency spectrum analysis that allegedly shows 'ghosts' in the track are quite likely to be hoaxes. The images suggest a full 24-bit audio source that radically exceeds the 8-bit audio depth of Gameboy tracks (not to mention the limited number of audio channels).
While the audio files in question really do contain those embedded images, the audio files are simply recordings of the original track in full 24-bit audio depth, with the 'images' added into them afterward (IE - they did not come from the Gameboy track).
You'll see what I'm talking about, here:
[video=youtube;nmZN7rbJLoc]http://www.youtube.com/watch?v=nmZN7rbJLoc[/video]
I can tell that my hearing is staring to go with age - there are tones there that I can just barely hear (though it's also possible my speakers are having difficulty reproducing them).
Honestly - I kind of like the uniqueness of the track. Though it took me years to be able to play through Jurassic Park, alone (wandering around buildings with dinosaurs waiting to eat you around every blind corner and through every door) - and that tone would have probably made getting through Lavender Town a bit of an emotional struggle for my young yellow self.
