There have been times, when as somewhat of a hypocondriac, I panic and begin to think I happen to be at the onset of focal dystonia. I'm going on 70 so for many of the issues of playing, the clock is running out. But I love playing too much to throw in the towel.
A couple of years ago I was fighting what I though was essential tremor and had a mild quiver in my sound, particularly on soft sustained notes in the mid register.
I learned that by using the large abdominal muscles when expiring, I was able to blow through it. Those larger muscles did not seem to want to quiver. A more shallow breath without the support from below the navel - and - oops. there comes the shaking. I learned something from a homeopath regarding what the Asians refer to as the "Chi" a spot below the naval which is believed to be a source of life's energies. I'm no expert, but when I take by breath from that area, and also keep the diaphragm from riding up, into the chest cavity, I am able to keep a large, soft or loud, resonant tone. I also found that using the tongue and accompanying syllable for sluring up or down, that that friendly smooth and flexible type of sound is much more easity attained.
Relating this to FD come when I realize that notes that just would not speak were really from a pinched air stream, which in not really all that much playing time was adding to the quick exhaustion of my chops. It was muscle exhaustion not FD. The best solution is rest. A couple of days off works wonders. So now while muscle exhaustion is a drag and very frustrating, knowing that it will go away in a couple of days with rest and good nutrition sort of calms my spirit.
So these days, the warm up is intent upon warming up breathing from the chi and allowing that breath to service just about every other aspect of playing. It really knocks me out at how easy tonguing, lip slures, long phrases, sudden dynamic changes have become. When you get up there is years, every little trick helps and it does pay off to play smart. What one thing that is very real is memory, both mind memory and body memory such as breathing etc. Particularly when some of these have been "relearned" at a later age. For the body and muscles to remember them is not easy. I find that I need to review them every day without fail, or I go back to grade school habits, which for me were not good. So there!!!
Wessex 5/4 CC "Wyvern"
Wessex 4/4 F "Berg"
Wessex Cimbasso F
Mack Bass Trombone
Conn 5V Double Bell Euphonium (casually for sale to an interested party)