Creepy, isn't it?
I must have spent close to three hours last night diving into the rabbit hole that are number stations. Why? You can thank a recent episode of Fringe for it, although why the station on Lost didn't get me thinking about it first I have no idea.
Anyway - number stations. For those who have never heard about these, they're shortwave broadcasts that come from often-unknown transmitters that are just what you hear above - typically some sort of identifying sound, tone, or song, followed by a series of numbers. To add to the creep factor, sometimes the numbers are read off by a man, or a robotic voice, or, such as in the video I linked above, the voice of a small child. They're most likely used by spies and government intelligence bureaus (if convictions of spies who had the key is any indication) to transmit messages using one-use codes of some sort, and the genius of it is in the simplicity of it - these broadcasts can be heard by anyone, written down and preserved by anyone, but only the person or people who are supposed to understand the message can because of how they work. It's utterly fascinating.
I gotta say, too - I spent hours reading and listening, and felt like I was doing something wrong. It was really kind of creepy and crazy, and still is. I went to bed last night and dreamed that I was busting a Russian spy ring. Most exciting dream EVER.
So yeah, I'm pretty much obsessed at this point. I found that Archive.org has the entirety of a bunch of recordings, named The Conet Project, which are a blast to listen to (the guy who, er, curated it is profiled here). The liner notes for it are beautiful, too - equal parts informative and conspiracy-nutty. Really great.