Bernhard, I'm still (patiently) waiting for a response.
Patience is a great virtue, and you shall be rewarded accordingly.

(Sorry, Will, I didn’t see your post

, but boy I am glad you asked.)
First of all, these things are almost impossible to write about without all sorts of misunderstandings creeping about. So it is well possible that if me, xvimbi, vladhorz, Mark and Alexander met to discuss the subject (preferably over a nice meal with some superlative wine

)and to demonstrate to each other what we actually mean by our words, my bet is that we would all end up agreeing.
Now for your specific questions.
1.
Hang on...Alexander technique speaks of the neck-head relationship and says walking is lead by the head. Also Thomas Mark says in 'What Every Pianist...' that when pianists move side to side and/or forward and back that 'the head leads' and 'the vertebrae follow in sequence. (p26)
Well, that may well be what Alexander and Mark say, but that is not how Bernhard understands it.
First of all, if you enquire on how Alexander came by his “technique”, you will learn that he was a Shakespearean actor whose acting career was destroyed when he found that he lost his voice every time he stepped on a stage. He went to several doctors and no one could help him or could find what was wrong with him, especially because out of the stage his voice was fine. So he was told time and time again that his problem was “psychological”, which didn’t help him a little bit, and made him pretty pissed off. Without anyone to turn to, he decided to tackle the problem himself. After several months of painstaking observation on a three way mirror, he figured out that the reason for his voice problems was very simple indeed: On stage, he would tense out of nervousness, his head would jut forward (leading by the chin so to speak), his neck would became badly misaligned with the rest of his spine, a misalignment so severe that it constricted the vocal chords and resulted in loss of voice. Having diagnosed the problem, he spend the rest of his life figuring out a solution (a brilliant solution, by the way). But as it is often the case with people who discover something deep about themselves, they become oversensitive to the problem: Alexander looked around and started seeing people from all walks of life with a neck problem similar to his. And then he did the big logical jump: Misalignment of the neck vertebrae is the universal problem.
Of course it is not. It is just one such a problem – shared by many people. There are all sorts of other misalignments causing all sorts of other problems. And as soon as you get someone figuring his problem is not round the neck, but round, say the wrist, a new “technique” comes into being. Hence all these diverse systems in body work. This is not very different from diverse piano pedagogical approaches each claiming to be the ultimate solution. In fact, they are the ultimate solution for the specific problem of the specific author who experienced them, and now he blows the whole thing out of all proportion.
Alexander people would do well to get out of the neck obsession and expand their horizons (a trend already found in many modern Alexander practitioners, like Michael Gelb), since the
solution found by Alexander can be applied to every single kind of misalignment. Not only neck ones.
As for moving from the head, of course many people do that. You can even say that in our society it is “normal” for the chin to pull the whole body forward. But “normal” does not make it “good” or even “desirable” (e.g. unhappy marriages are “normal” but are they desirable?).
Now, I come from a different tradition altogether: the tradition of martial arts. In the martial arts you must move from the spot four fingers below the navel (Chinese: tant’iem or Japanese: hara). I suggest you read about it here (or even better, ask an aikido – taichi teacher to show it to you):
https://pianoforum.net/smf/index.php/topic,3396.msg30084.html#msg30084(Laziness, the 3 centres and how to use visualisation to deal with it – consciousness and its location – applications to martial arts and piano playing – locating the consciousness at the movement centre).
https://pianoforum.net/smf/index.php/topic,2814.msg24872.html#msg24872(How a student’s physicality affects teaching – discussion on arm x fingers – moving from the centre: tantien and taichi – Seymour Fink gets discussed as well)
https://pianoforum.net/smf/index.php/topic,2809.msg25013.html#msg25013(Body movement – comparison of piano playing and the martial arts)
But you need to experience this sort of thing; someone must show you, and you must train and practise it, since in our society this is not “normal” or what comes “naturally”.
So contrary to what you say Mark and Alexander say, I would say that you move from the basis of the hip (not from the head), and the vertebrae follow on a bottom to top direction, instead of a top to bottom direction (the head leading).
Now, that is not to say that it would be impossible to move from the head. The question is, is it desirable? To answer it, the only way is to try both until both feel equally comfortable (this is an important point: they must feel equally comfortable otherwise unfamiliarity may be confused with optimum ergonomics) before you can compare them. This I know: move from the head in a judo hall, and you will consistently find your head level with your body resting on the mat. Move from your tant’iem and you will very rarely be thrown.
Anyone care to expand on what they know about the origins of body movement? What movements at the piano (if any) are not initiated from the body's centre?
The human body is very adaptable and flexible. You may have had the opportunity to see handicapped people who could draw and write with great fluency and perhaps even better than a normal person, by holding pencils/brushes with their toes. You can originate movements in all sorts of way. There is not a single origin. However, that is not to say that all movement origins are equally optimal, or desirable. Sometimes, you have no choice (as the handicapped people mentioned above) and you have to do your best with the resources you have. So what I am saying is not that movements can only originate from the centre, but that
optimal, injury free movements always start from the centre, and we should educate ourselves towards it – not only in piano playing, but in every single activity that requires motion of one sort or another.
Thomas Mark says that no torso weight is delivered to the legs, and that the legs are free to move. (p47) Thomas says the feet can be anywhere. Who to believe and why the difference in ideas? Both men seem extremely knowledgable...
Well, let us not worry too much about what Mark says, what xvimbi says, or what Bernhard says. Why not do a simple experiment? Go to the nearest ice-cream parlour, the kind that has those high stools where your feet can dangle in the air. Now order your ice-cream and try to eat it, while balancing on the sitting bones and having no weight in your feet by letting them dangle freely in the air. Is it possible? I guess it is – I have seen artists at the Chinese circus do more impressive balancing acts – but is it desirable? Is it comfortable? Is it optimum? Surely not. Look at the people around you at the ice-cream parlour. Some will have stabilised themselves by having their feet on the iron-rail below the counter. This is fine and good – that is what the rail is for. Some will have their feet tucked under the stool on the iron ring below the seat (that is what it is for), however, these guys will invariably be crouched forward stabilising themselves with their elbows, since with the feet tucked under, the feet cannot take part of the weight of the body in any efficient way.
This poses a especial problem for children learning the piano - invariably the bench is too high and they cannot reach the floor. You must have a stool under the piano for them to support their feet, otherwise they will be dangling in the air, and typically they will drop their wrists to stabilise their balance, and in consequence their body weight will be supported (partially) on the heel of the hands. Tucking the feet under the bench will result in the same problem. Is it impossible to play the piano in such a fashion? Surely not – Glenn Gould managed it beautifully (he also crossed his legs). But is it a good example of body use? Surely not.
As for “no torso weight being delivered to the legs”, this is like Aristotle’s statement that women have less teeth than man. Either Greek women are different in this respect, or Aristotle never bothered to count. Shall we do another simple experiment? Get one of these bathroom balances, and put under your feet as you sit down at the piano. Check it out. Does it say 0 (zero) Kg? I somehow doubt it (certainly mine doesn’t - in fact, see if you can play the piano and have zero kg on the balance). The legs are free to move, in the same sense that legs are free to move when you walk, but that freedom comes at the cost of transferring your weight alternately to each leg. It is not the freedom of dangling your legs. Not even Glenn Gould could manage that.
However, as I said in my first paragraph, I doubt very much Mark is really meaning what he is saying. Probably if asked, he would elaborate on his writing and your understanding of his words would likewise change. This is, of course, not a criticism of Mark, but pointing to the limitations of verbal descriptions. So what you may have here may not be a legitimate difference of ideas, but simply a different way of talking about the same (or similar) ideas. Then again, like Aristotle, Mark may be simply wrong. It is the result of the experiments that count, not what this or that knowledgeable authority says about it.
I understand the flow from shoulder to finger, could you please explain how energy can be transferred from the hips?
I can state it, and I can demonstrate it, but I am not sure if I can explain it in a way that would be satisfactory. Keep in mind Richter’s statement: “I played that note with my big toe!”
(How could he do that if his legs were dangling freely in the air, I wonder

).
Best wishes,
Bernhard.