His playing of two guitars at the same time and then the playing of the guitar with the violin exemplifies everything that it could.
It's attacking the pompous AND the mindless, the "rock as art" AND the "rock as throwaway" all at once. It speaks to ambition and ego and, in short, it's an exact mockery of the entire ROCK AND ROLL mindset (note: that's "rock and roll" in caps).
And by the way my favorite moment in particular is when Nigel suddenly notices the violin isn't quite in tune to his liking and has to fix it.
[As an aside, I have to believe, though there is no proof, that the violin is picked as a reference to Jimmy Page who would sometimes play his guitar with a violin bow. If Jimmy Page can play a guitar with a bow, Nigel Tufnel can play a guitar with a violin.]
Having said that, and looking at how playing two instruments at the same time can be stupid, let's face it, playing two instruments at the same time is generally awesome. I'd love to play ONE instrument at all let alone be able to play multiple.
Which brings me to Johnny Greenwood (guitarist Radiohead) and a video I just rediscovered recently. Greenwood is an extraordinary musician. He's a man who can can play virtually any instrument (or any object that makes some sort of noise), he can compose and score music for orchestras and, of course, he can shread a mean guitar. In this particular live version of "Street Spirit [Fade Out]" he plays both the guitar and the keyboard. Beside the fact that this is impressive by definition, this isn't all that impressive: that is the song is quiet, ethereal and open, there isn't that "100 miles a second" playing on either instrument that turns it into "a feat". But towards the end of the song, the video shows something interesting: he's not just playing the keyboard AND the guitar, he's playing the keyboard WITH the guitar. Rock and Roll.
[Disclaimers: I regret the association between the two linked videos though I felt it unavoidable. I believe "This Is Spinal Tap" mocks everything bad about Rock 'n Roll while Radiohead represent all that is good. I also regret focusing so much on just the multi-instrumentalist portion of the video as it is a perfect rendition of a perfect song and I've probably distracted from it's pure beauty. I also wish to restate that the playing of guitar and piano in the displayed video doesn't represent any circus-trick level of musical prowess. I just think the idea is awesome in itself. In short, this whole post is a mistake and I can't find the delete buttonm. All rights reserved.]