I just happened upon this trick when testing what it was like filming from inside my guitar. *Note this effect is due to the rolling shutter, which is non-representative of how strings actually vibrate.
• You must have the strings brightly backlit to get the camera to capture at such a high frame rate (pure conjecture). You can see how the effect fades when the buildings come into view.
• Use a pencil
*This was used with the front facing camera, try the back camera, it may capture better! (tried it, it didn't look as good for me)
There is a heated discussion with *real science* over at reddit
*UPDATE here is the 'tracklist'
:14 - "Tears in Heaven" by Eric Clapton
:56 - "Signe" by Eric Clapton
2:57 - Snippet of "Tomorrow Land" by John Scofield
- the rest is just noodling around.
Also, I never thought I'd be known as a 'youtube guitarist', I just play for fun- I'm actually a motion graphics designer/animator. Check out