I notice when watching videos of Gary Moore, Joe Bonamassa etc they have the same tone and sustain on the 20th-22nd fret as the do on the 2nd or 12th fret. I have an 89 standard and several other guitars and whenever I play up on the higher frets on my guitars the tone and sustain dies faster than when playing on the lower frets. Does anyone else notice this? Is there something I can do to maintain the tone and sustain on those 20th frets?
I Think what your missing is a line of VERY LOUD amps being played at large venue volumes. When amps are turned up this way, they create resonant frequencies (ie feedback) that allows a guitar to resonate due to the air waves around it helping the guitar to vibrate at the same freq. as the note being played.
This is a basic way of explaining it, but I am assuming you arent playing for thousands of people and turning up the amps enough to MOVE AIR the way that Joe B and other artists do...aside from them having the top quality setup and instrument.
Try turning your amp waaaay up to 7/10 or more and you will start to hear the guitar pick up sustain simply because it is helping itself to vibrate at that freq. in real time.
This is my explanation...
try finding a good compressor set correctly. this can help fill in the gaps and allow your notes to sustain longer without the added volume.