rojcewiczj wrote:Its seems to me that the concept of "setting" the bones is closely related to that of Song.
No, not really. You are making this much more complicated that it needs to be.
For some years, I used to see a chiropractor for problems with my neck and mid-back. After I began studying Taijiquan and was able to "relax" sufficiently, I no longer needed a chiropractor: I can "fix" my own back and neck simply by standing for 20 minutes. Doing so without excess muscle tension allows gravity to realign what needs to be realigned. I don't need to "set" anything, just stand there "properly": gravity does the rest.
At its simplest, song/fang song is to let go of excess muscle tension and allow gravity to "lengthen" stuff. Taijiquan is an art of "lengthening".
I have often heard the phrase to "set the shoulder".
And, what, exactly, does that mean?
Without knowing exactly what it means, what you have to physically or mentally do - or not do - it is a meaningless phrase, much like the phrase "opening the joints" can be.
It seems to me that the correct setting of the joints allows weight to flow effortlessly through the bones. When one relaxes, one can feel if there is discontinuity in the joints, where there is an inability for the weight to settle through the bones. Over time, one can make self-corrections to the bone alignment through exercising the joints. At a high level, one can make a full and instant transfer of weight through the bones, regardless of the contact point. Is this a part of what Song seeks to achieve?
I think you are barking up the wrong tree. Force exerted on the body propagates through the body's skeletal structure. Muscles and connective tissues hold the bones in alignment, else we'd crumple to the floor.
As Bao stated earlier, we want to learn to relax/deactivate muscles that aren't directly contributing to maintaining a desired structure (or performing a desired action). As another beginner's exercise, I ask students to stand feet shoulder-width apart, hands at their sides. I'd ask them to tense every single muscle they can - eyes, face, neck, arms, hands, legs, abdomen, toes, back... I'd then ask them if doing so helped them stand any better - that is, resist the force of gravity acting on them. Next, I'd have them relax every muscle they can while still remaining standing. The point of the exercise is to demonstrate for them that engaging "lots" of muscles that don't contribute to a particular action or activity doesn't improve their ability to perform that action. It tires them out, while contributing little. (It can also result in other undesirable things, but that's beyond this discussion.)
It is important to become self-aware. By doing so, one can begin to identify muscles that are engaged that aren't helping a motion or posture. "Poor" posture, generally, involves engaging muscles to counteract the poor posture. One of the ways of reducing excess muscle tension is to improve one's posture. To do so, one has to either recognize a poor posture and/or excess muscle tension. Without self-awareness, neither of those are possible. Many people are unaware of their poor posture/alignment and take the excess muscle tension that counters it to be "normal": it is what they get used to and is why many need to have it pointed out to them.
If you want to go "all-traditional", qi and jin get "blocked" and their transmission through the body "broken" at places of excess muscular tension/poor alignment, common locations of which are hips and shoulders. (Lower back is also a common one.)