I ad seen this before but had forgotten how fantastic it is. Yes, the quick tune-ups are fantastic, but the facial expressions at just the right moments are priceless.
i love this sorta stuff... i remember years ago my brother showed me one of Eric Clapton playing, but was overdubbed (obviously) with all sorts of weird noises and gaffs and blunders. hilarious!
here's another that i can't help but snot-bubble to...
I cried laughing at some of the earlier "shred" videos where they overdubbed terrible playing onto some of the guitar gods. The one for Vai's Tender Surrender was magnificent.
But I think all of those got taken down, which was a major loss for humanity.