A few thoughts after some days of intensive practice. My focus has been awareness of tension, since I have a few sore points on my hands due to an old injury. One concept from yoga has helped me. According to what I have learned, the arm structure is considered an open system, whereas the legs are a closed system due to the fact that they end with the feet on the ground (at least when standing). In flute playing, the arms are also sort of closed system; they end with the fingers on the flute. But I like to imagine that in spite of that, they are open systems. Just that feeling that they could continue to extend if they wanted. Same with the legs while performing, even though they are grounded, I like the idea of them being an entire structure that could extend if needed.
It is very important for me to think of extension not only as motion away, but with a twist. Pretend you have a knob that’s straight in front of you and just beyond your reach. Bring your right arm out to reach for the knob. Bring your shoulder blade from the back with you while reaching out, but make sure the shoulders are not raised. Rotate the entire arm outwards (as if you want to turn the knob to the right with your whole arm). Then, leaving your upper arm (the part nearest the shoulder above the elbow) as is, rotate only the lower arm and your palms in (as if turning that knob back to the left). Then bring the arm into playing position (let the shoulder blade come back with the arm). When I do this, I have a better feeling of security and freedom. Repeat with the left arm, first turning the knob to the left with the entire arm, then back to the right with only the lower arm.
The other thing I have to tell myself is not to get tense about tension. If at the end of a phrase I notice my leg is stiff, so what? Just unstiffen it and get on with it. The point is, I noticed it. I have to remind myself this is a process. If there is time, repeat the passage with better awareness, to find out which action made me try to support with my leg. And then hopefully laugh at my ridiculous notion that a locked knee can help with my high note. Better than beating yourself up.
And Mula bandha really helps! (It is NOT the squeezing of those other cheeks that some refer to.) Awareness of the pelvic floor is a positive way to exercise awareness, to get away from being too vigilant about the negative or unproductive things. I once had a male flutist tell me “but I don’t have a pelvic floor” and I was gullible enough for a microsecond to actually look down to see if his insides had spilled out onto the ground from between his legs. Guys, you do have pelvic floors. It is part of the blueprint for human anatomy.