Sorcery

See, this is what happens when people listen to jazz.

If you watch a guitar string vibrate with a TV screen in the background you will get a similar effect.
I just tried it with my computer monitor and it didn’t work. But our old cathode ray TV does it. I think it has something to do with the scan rate.

It’s a form of Aliasing http://en.wikipedia.org/wiki/Aliasing
Simen (above) has it right, its the same as the ‘wagon wheel effect’ in films. Funnily enough, your own eyes can alias spatially at the edges of your vision; if you look at a black/white grille (like the top of an electric heater perhaps) at the very corner of your eye, you might notice the apparent spacing of the grille get larger. This is due to the reduced density of light sensing cones at the edges of the retina, giving effectively a lower sampling frequency.

Actually, you don’t need a high capture rate – you just need the frequency of vibration to be close to an integer multiple of the sampling rate.
Say a sampling rate of 25 fps and a note a little below middle C at 251 hz, and you would see a sampling-effect vibration frequency of 1 hertz.
As the gap increases you get odder harmonic effects (“beat patterns”) where the magnitude of the underlying vibration itself appears to osscilate, then returning to simple slow vibrations as the frequency approaches the next multiple of the sampling rate.
Of course if the vibration is precisely a multiple the sample rate you see no motion at all.

Here you go! http://www.break.com/index/helicopter-blades-stop-moving.html

I just read that the brain has frame rates too, but each portion of the brain has different rates, and one part of the brain coordinates the incoming signals so that we can perceive cause and effect in the right order.
The theory is that in the schizophrenic brain, the signals don’t get processed in the right order, so a schizophrenic might hear something before they see it, on the TV, for example, which would provide the illusion that the TV people are extracting content from your brain.
http://www.sott.net/articles/show/195379-Timewarp-How-your-brain-creates-the-fourth-dimension