Hi snyprrr, how's the piece coming along? I was listening to a new recording of Ginastera's sonata for guitar today and thought it is something you should definitely check out. The Scherzo in particular uses lots of extended technique for the guitar including lots of percussive effects. CDs are pretty easy to come by but the score you would have to purchase. Don't have it myself or I would send it.
I've been meaning to get back to you. Might as well do it here!
Your first note gave me a lot to think about. As far as percussive, I realized you might be implying the use of any foreign object,... this of course would expand the percussive palette. For my purposes, I'd like to concentrate only on what the hands can do. For that reason, I offer:
1) Nails on the body
2) Fingers on the body
3) Palm fat on the body
4) Fingers/Nails on the neck.headstock
I must be missing something? I just have been banging around on the thing, and I just don't think I'm getting that many DISTINCTIVE sounds. The dull thud of the palm, or the click of a nail, of the rat-a-tat-tat of the fingertips,... but what am I missing?
Finger taps on the top of the body, to me, don't sound that different from finger taps on the SIDE of the body,... or the side of the body and the neck,... in a concert application, are these sounds really that distinct?
One thing I have been considering is a foot stomp along with a palm/body thud, as long as the shoe/floor situation yields a proper sound.
One thing: there may be a lot going on, where a tap/thud is only going to be one sound amongst many (string snaps, harmonics, other special effects), so, 2-3 generic percussive sounds (that are distinguishable from one another) might be all that's needed.
btw- I will check the Ginastera.
Another thing that appears to be developing in this piece are the different ways of 'scraping' the strings, which, on a classical, really only works on the 3 bass strings. I've been working on the 'long scrape' (similar to what rock guitarists do with the pick scraping down the string), the 'variable speed slide', which makes a high, whistling sound when your finger slides up and down (this is that 'unwanted' sound when we switch positions), and the 'short scrape' on E6, which sounds like a creaky spring.
On the top 3 strings, running your fingers up and down them yields a sound similar to breathing (if done in an 'in/out' manner), which is definitely making it in (though, this takes the piece into dangerous territory as per execution).
As to our initial mss.,... did I mention Elliott Sharp? Punch in 'Elliott Sharp solo' on YouTube and check that viddie out. He has some interesting ideas (though he uses open Eb tuning, so it's easy), but he also appears extremely sloppy (compared to a classical guitarist). At first I was conquered, but, after a while, I got what he was doing.
Also, what do you think about plucking the fretted string from the Nut side of the equation (instead of from the Bridge/normal side)? You can still get tones,... I just wonder if all classical guitars will have the same scale?
I'm reeeally lazy, and already I have written A LOT of notes on paper (first draft),... oy!,... how do they do it???

discipline, discipline, discipline