About the racket this man is making

[soupymess]

From 3:58-4:06 in this: http://youtube.com/watch?v=ReW9uUYm-DA&t=3m50s

That... dampening, I'll call it.. where it gets all frenzied and blurry - is that effect more likely some kind of guitar savant trickery or a fault of the recording? It settles down after this last 'burst' which may or may not point to it not being accidental. What's going on there?

 

[Peripheral Visionary]

I'm not sure what you mean by "dampening." He's got it tuned to an open D (D-A-D-F#-A-D)
and the arrangement employs some of the lows string in a constant modal "drone," that is common in Appalachian mountain music, especially with a mountain dulcimer.