Tim,
Jim has elaborated on some great points. Just picture in your mind how LARGE Stevie's hands were. Watch his videos. See how his hand could wrap completely around the neck of the Stratocaster. His thumb could have touched the far side of the neck I'd bet! Now imagine those big hands laying hard into the piano wire guitar strings he had strung on his guitar, playing through a very loud and mostly cleaner than we think Fender Vibroverb or Dumble amp. His sound most definately came from those hands and how hard he hits the strings and how thick the tone was coming from this setup. It's a combination of all that along with Stevies own SOUL pumping into his guitar like a live wire coming at us at full voltage! He did this every night he played. He never "saved his best performance for the folks in Hollywood or New York"...he was always on. Even in foreign countries he played in. He gave his all and you can hear it and see it. THATS what it means when someone has an identifyable technique and sound.
Not long ago I emailed Robert and told him that even when he plays high gain stuff on his demo videos he still manages to sound like himself. Clean or dirty, if I closed my eyes I could easily tell that it was him playing. Its the WAY that he plays (along with his set up) but it's more about his picking style, his hands, how hard he plays or how soft, his PHRASING...all this. Reread Jim's post above about picking styles. I bet if we all hung around together in real life playing everyday for a period of time we could pick out who was who just by closing our eyes and listening to each of us play. Jim gave technical specifics on achieving tone and the various ways to do this. I'm inputting the human aspect of it...learn to hit that puppy HARD or soft when you feel it. Get your body into playing that guitar. Sit, stand, walk jump...your tone is gonna try to change in different positions but if you're genuine and really play from your heart and soul you'll come up with a tone of your very own and what a tone that will be Tim.
Guitars/Bass - MIM Fender Classic 50s Strat, MIM Fender Standard Strat, Squier Classic Vibe 50s Tele, Gibson Les Paul Studio, Epi '56 Gold Top Les Paul, Martin DSR acoustic, Sigma Martin Auditorium electric/acoustic, Squier Jazz Bass.
Amps/Cabinets/Modelers - Model 2558 50 watt Marshall Silver Anniversary Jubilee combo w/ Celestion Vintage 30s, 4x12 Marshall cabinet w/25 watt Greenback Celestions, Fender Blues Junior w/ a couple of Billm mods, Line 6 POD 2.0, Roland Micro Cube
Pedals/Effects - Cry Baby Classic Wah, Boss TU-2, Boss NS-2, Boss RC-2 Loop Station, Ross Compressor, MXR Micro Amp, Danelectro FAB Echo, Danelectro FAB Chorus, Danelectro Chicken Salad, Marshall Guv'nor Plus, Marshall Echohead, Duhvoodooman's Zonkin' Yellow Screamer, Digitech Digiverb, Digitech Bad Monkey, Dunlop Fuzz Face, Homemade Loop Bypass pedal, Duhvoodooman's Sonic Tonic (Maxon SD-9 clone +), Voodoo Labs Superfuzz