Weight, by definition, is a force that acts in the direction of the gravitational field, i.e., towards the center of the Earth (which would be straight down, for us people living on the surface of the spherical Earth). If you're not talking about weight, then don't use the term please.

I understand that its not pleasant for the others to watch this discussion unfold.. however, I think we have somebody here who claims that all he says comes directly from the laws of Physics and from pure math. I know for a fact that they do not due to the many inaccuracies in the terminology used (one such example is pointed out in this thread)and due to the constant inability on his part to come up with any substantial mathematical proof or even Physical proof for any of his claims which are all based on some very iffy analogies made between the arm and a taut chain (if you care to look at how the bones are aligned, you will soon realize that its far from a chain but he doesn't care) because its not just these joints, its also a lot of muscle in there that pulls and tugs at all these bones. So the tension in these structures is simply impossible to calculate based on a model of a single chain or a single string. None of it is scientifically sound and we have young people on these boards responding to some of these with "I will try it out as it sounds interesting". I don't like seeing people misguide others who might not have the sufficient training to discern science from pseudo-science.

You are right, the weight acts in the direction of the center of earth. The shoulder and elbow are pivot points causing the elbow to move back when the forearm is dropped, if you play with your elbow in front of your body. I'm not sure of the terminology that describes this force (centripetal maybe?) but it is separate from gravity. I think a truly definitive discussion of this would be pretty dry reading.

It would be dry reading but that was not the intention. Here's somebody who claims to speak in the language of Physics. All I'm saying is, at least use terms as they should be used, so that people can understand this stuff. All the assumptions that go into his theory make it shaky enough. Why then talk of "weight" and expect people to know that what he really means is something that's entirely different from the WIDELY accepted notion of a weight? If he doesn't intend for people to understand it, then I guess its ok to have your own definitions of weights and forces.

I chimed in because somebody else talked of a weight and I'm pretty sure he meant it in the conventional sense (the only sense of the word actually) and the response was "the weight does not act downward". How can somebody expect to hold a conversation after that?

Indeed, I should have specified the "resultant force" of the gravitational force. However, the important point is that (in full release) this resultant force acts primarily horizontally, due to the angle of the standard setup. To assume that gravity primarily induces a downward resultant force at the fingertips is inaccurate and can lead to substantial pushing (attributed inaccurately to weight). Above all, the hand is pulled backwards. The experiment I gave gives a very clear illustration of how the force that balances gravity is primarily horizontal.

I'd just stress that it's definitely not "separate from gravity"- as without gravity no such force occurs. However, as you say, I think the pianistic issues and implications of this are rather more interesting than worrying about whether I was careless enough to omit reference to it as a resultant force, while typing in haste.

Lets get this clear: gravity, always produces a downward force, whether its at the fingertips or at the tip of someone's nose.

What you're talking about is the component of this force along the direction of the finger (because the finger makes an angle with the vertical).

Before we talk about the components of different forces, lets lay out what forces exist in this situation:

1) Gravitational: Weight of the arm ALWAYS acting downwards.

2) Muscular forces: Unknown direction (unless you do an extensive study and find out the exact directions the various muscles pull towards). However, at the finger tip, this force acts primarily along the direction of the finger (I'm not a 100% on this, I need to know more about which muscles and how exactly the finger is caused to move), the rest of the muscular forces get absorbed in the joints, etc. So to summarize: muscular force (after losses in the tissues) act in a direction along the direction of the finger (open to debate).

3) Reaction forces from the keyboard. Newton's 3rd law. They act in exactly the opposite direction as the force applied. These needn't be equal in magnitude to the sum of the other forces (in the opposite direction) because we are not talking about an equilibrium state.


Finally, a HUGE inaccuracy in what you just said: "the resultant force of gravity, acts in the horizontal direction". Think about it for a minute. A force (that you admit now) that acts downwards cannot have a component in a direction that is perpendicular to it. So there is no resultant force of gravity in the horizontal direction if by resultant, you mean component.

If by resultant, you mean weight-reaction forces, that again cannot be in the horizontal direction for the same reason.

You can respond to these one point at a time. Talk Physics. When you mention gravity, and reaction/resultant forces as being caused due to it, none of these forces can be in the horizontal direction. Not in this universe as we know it.

EDIT: I forgot another important force: frictional force. That is what balances the horizontal component of the "muscular force" (whatever force not due to gravity, that transfers to the key via the finger) so that the finger does not move in the horizontal plane.

Resultant force due to gravity, granted (whatever it means). Hope you weren't careless this time. Read the above post to reveal a huge problem with what you just wrote about it being horizontal.

If you're trying to confuse me, you're failing. I've studied nechanics. I have no idea what particular point you are implying about reaction forces, but these are specifically factored into the balance of forces. They replace what the other arm does, when you transfer it to normal playing. I mentioned them in this very thread. Also, what leads to you believe that I have forgotten friction? In what way does that compromise anything I have referred to? If you have a point, I'd prefer if you went ahead and made it- rather than speak so generically.

I didn't say that gravity has a horizontal component and you know as well as I do that this is entirely beside the point. We both know that gravity is responsible for the horizontal force that brings a pendulum sideways. Remove the gravity and you remove the sideways force and motion. If you're interested in this, would you mind discussing something of pertinence with regard to how this translates to the balancing of forces in a practical context? In terms of how this affects piano playing, it is of no concern to a non-physicist to have their time wasted upon the details of how gravity results in this effect.

As I say, if you have a specific point (with reference to the specifics of what I have personally set out) then make it. I'd be all ears. However, I have no idea as to what a mere list of terminology (within which I assure you that nothing is faintly alien to me) is supposed to contribute to anything.

Are all of these large scale mechanics even applicable to such a complex system as the human playing the piano? There certainly is no real right answer...no matter how rigorous or accurately you can prove the mechanics of "correct" playing, what matters is how the brain of the player interprets it and plays.

I might tell somebody to "relax" when playing repeated octaves, and "relaxing" is technically impossible. But the key message is to try to reduce buildup of tension so that the octaves don't sound laboured and your wrist isn't dissolving in the resulting lactic acid. Serious, the amount of effort required to precisely model and communicate the exact mechanics of playing isn't even worth it...

That is what balances the horizontal component of the "muscular force" (whatever force not due to gravity, that transfers to the key via the finger) so that the finger does not move in the horizontal plane.

Well, that is based on some MAJOR (rather unscientific) assumptions. That only follows if we assume that there are no forces acting to pull the hand backwards.

Am I to take it that you believe it is impossible for the reaction force to be pulling the arm forwards and for gravitational release to be balancing that (via backward pull at the wrist)? If so please elaborate.

I didn't say you forgot about friction (even though you don't mention any of these forces anywhere except to keep repeating that gravity somehow creates a horizontal reaction/resultant force which is farthest from the truth as anything can be).

Gravity does NOT have a horizontal component in the case of a pendulum swing. If you've studied mechanics, you wouldn't make statements like these, one after the other. The gravitational force ALWAYS acts downwards. There is a fixed rod in which there is tension. The tension equals the component of the gravitational force along the direction of the rod (and is opposite to it in direction) so that the forces along the rod are balanced. The pendulum bob does NOT move horizontally, it moves tangentially to the path (if you trace the path). The forces acting here are frictional (air resistance) and a component of the weight along the tangent direction. NOWHERE does gravity make anything move horizontally.

At the bottom of the trajectory, the acceleration is zero. There is no resultant horizontal force at that point. The velocity though is finite due to the momentum and that carries the bob to the other side. As soon as it gets to the other side, it starts decelerating now since the component of the gravitational force along the tangent is opposite to the direction of motion.

Finally remove gravity and you remove the sideways movement: firstly as I mentioned, the movement is NOT sideways (horizontal). Remove gravity and you remove the tangential motion. Yes, so? What does this have to do with the finger playing a key situation? If you were trying to prove that gravity causes SIDEWAYS (horizontal) motion, you have failed yet again, as Newton has condemned you to.


How long ago and where did you study mechanics?

That's where I disagree. I don't believe that it's necessarily very complex at all, most of the time. I believe the assumption that it must be complex is inaccurate. If the finger pulls a key from a point of stabilisation (created by release of the upper arm) causing a taut chain it really is easy. The finger pulls and remains stable, without internal tensions in the arm. Still, but not tense. It's a very simple approach, that does not prevent you from also using more complex motions- should you feel a need.

If I hadn't learned a substantial number of practical applications from this, I wouldn't be writing about it.

Reaction forces can have horizontal components, but none of those reaction forces would be due to gravitational force as all the reaction forces that can be attributed to gravitational force must necessarily be upwards.

The reaction forces that can have horizontal components would be forces that are REACTIONS to all the forces exerted on the key that have a horizontal component. Its the third law, as simple as that. If you exert a force in a certain direction, you get a reaction in the opposite. Gravity = vertical. Reaction to gravity = NOT horizontal. Other forces = any direction not vertical, thereby having horizontal components --> reaction forces due to these other forces = equal and opposite to those forces, hence horizontal albeit in an opposite direction.

Still confused?

That, coupled with a total disregard for basic Physics, is why your theory won't work. Sorry, I call a spade a spade.

All this ought to be freshman Physics. I can't spend anymore time explaining this to you. Maybe you should get yourself a copy of Resnick and Halliday. They have very nice illustrations that will help you understand this better. I'm serious. Good night.

Gravity does NOT have a horizontal component in the case of a pendulum swing. If you've studied mechanics, you wouldn't make statements like these, one after the other.

Did you notice that you quoted this from me:

"I didn't say that gravity has a horizontal component"

in the same post? If you're not going to read what I'm writing, please do not reply at all.

The gravitational force ALWAYS acts downwards. There is a fixed rod in which there is tension. The tension equals the component of the gravitational force along the direction of the rod (and is opposite to it in direction) so that the forces along the rod are balanced.

Am I supposed to sound surprised? I know that. I am not interested in a pedantry debate. Please tell me why you feel anyone needs to know that- rather than notice that release of their upper arm allows gravity to draw their hand and elbow backwards?



Finally remove gravity and you remove the sideways movement: firstly as I mentioned, the movement is NOT sideways (horizontal).


I didn't refer to a pure perfectly horizontal movement. I said that it mostly pulls the arm sideways- not "it pulls the arm perfectly sideways with no down element whatsoever" It does. What is this supposed to add, presently?

I am not interested in seeing who can quote the most unnecessarily in-depth explanation of something that has no consequences, with reference to piano playing.

Reaction forces can have horizontal components, but none of those reaction forces would be due to gravitational force as all the reaction forces that can be attributed to gravitational force must necessarily be upwards.

?????

Did I specify reaction to gravity? Why such colossal and unprompted assumption about the fine details of what go into this? First you assume that the arm is held in position, without any release creating any form of resultant force upon the wrist. Now you assume that the only reaction forces are supposed to be attributed to gravity?

Where are these unfounded assumptions coming from? If you want to pick holes in this, I suggest that you read my blog and see specifically what I'm actually talking about- rather than leap to your own assumptions.

You are not supposed to sound surprised, but you are also not supposed to make that final statement. Gravity cannot be the cause of drawing the hand backwards (horizontally). It can only be the cause of vertical motions, whether upwards or downwards. If you want to talk about horizontal movements, you need to quit using the word "gravity". You gave the example of a pendulum that does not even move horizontally to prove your point. I gave you specific details of that motion explaining why you were wrong. You choose to downplay it. You are simply not interested in the Physics at all and I think its quite shameful because I do think you deserve credit for trying to think of this differently, with the model of a chain in mind, but if you are to progress, you need to do better on the Science. If you do not want to listen to any Physics that argues against your statements, it tells me that you are simply not interested in meaningful debate, so be it.

As david_a pointed out in another thread, you hope to tell people what to do and present it in the guise of science when it is nothing but somebody just trying to shout hoarse thinking that repeating the same thing over and over again and possibly louder each time will make the theory more valid. I'm sorry, it doesn't work that way. For all I know, what you say about the end result may have merit but nobody sensible would know that until you start being true to the Science. If you say that people don't need to know the mysterious science behind what you're saying, then at least don't say things that don't make sense Physically. Also don't say it all comes from Physics. Just say "I think this works, so do it, try it and let me know if it works". If you seriously hope to justify it based on the laws of Physics, you don't have to come up with your own laws of Physics, I hope you know that.

You can carry on as you wish. I've made my point.

If you removed the force of gravity, would such an action still occur? No. So gravity is the cause. I rest my case. The technical explanation irrelevant to anyone who is simply seeking to improve their piano playing. The resultant force of the release of the whole arm's gravity as a whole is PRIMARILY a backward force upon the hand- NOT a substantial downward force. You can feel this by balancing it out.

If you have a problem with that then please explain it.

If you seriously hope to justify it based on the laws of Physics, you don't have to come up with your own laws of Physics, I hope you know that.


I am not "justifying" a random approach, with physics. I DERIVED this approach using very basic physics and it has worked in a way that corresponds entirely with expectation- with myself and with students.

If you have any serious interest in this then by all means go ahead and prove that it is impossible for the resultant force that a released arm exerts upon the hand to be balanced against the reaction force pf finger action. I should very much like to know the specific basis for this belief- rather than see generic issues of physics that I am already familiar with quoted out of any evident context.

The simple answer is yes (surprised now? The technical details are contained in the posts above that you thought were irrelevant but I knew precisely where you understanding of this was lacking, which is why I went to great lengths explaining all that and sure enough, all of that fell on deaf ears). I'll spare you more technical details, just as you spare the "common people" out here the technical details for all the wrong statements that you make.

Technical details for others who might be interested: Any horizontal resultant/reaction forces CANNOT be attributed to gravity. In the absence of gravity, if you push against a wall, you will feel a reaction force in the opposite direction (i.e., horizontally, if you push horizontally). Similarly, on a piano key, there are forces traveling through the finger tip (all the forces other than the weight) which have horizontal components. To keep the finger from slipping, these horizontal components must be balanced by frictional forces. Frictional forces come from electromagnetic interactions. Basically interactions between charged particles on either surface (surface of the finger tip and the surface of the key). There are also reaction forces that oppose the forces transferred via the finger (when I say forces, I always mean all the forces other than the gravitational forces). Those have horizontal components because the finger makes an angle with the key.

To simplify and illustrate this, hold your finger absolutely perpendicular to the key. Make sure you exert a force only downwards. Does it make your arm move backwards?

Now have your finger make an angle with the vertical (that is, do not hold the finger absolutely vertical). Now push on the key.

Gravitational forces in both cases are exactly the same. The arm moves back only in the second case. Its a simple inference from there, I don't even need to say it.

If you're intent on being pedantic, you really ought to pay more attention to what I am writing before replying. I specified a few posts ago that I am not attributing the balancing reaction force to gravity. Do you take me for a fool? It comes from the finger's activity. Need I remind you again that I am referring to a RELEASED arm- not the held/pushing arm you signify in your examples (after all, both situations would have the arm falling backward, if you actually released the necessary push into the keyboard)? I stated as much very explicitly earlier in this thread when I set out the premise you have been attacking me for. If you're simply intent on arguing for the sake of it, please do me the courtesy of first clarifying what you are arguing against.

You keep saying that gravity is responsible for pulling the arm backward. I was arguing against that. Now you seemingly agree with me in a prior post.

Do you know what pseudo-science is? When attacked from one angle, it takes the opposite stance (because the theory is flexible enough to do that). When you then attack it there, it shifts back again. Basically a pseudo scientific theory is not falsifiable.

Anyway, I'm off to bed now as this is not worth the effort but I wanted to put all this out there in writing so that anybody who reads your posts also gets a view of things as they really are.

Read the posts earlier in this thread. Nothing has changed but the strawman you are arguing against.

I'm still waiting to hear what your actual point is. Was it exclusively the pedantry about the horizontal movements and forces that are indeed caused by gravity's action upon the chain of joints? Or do you have anything notable to contribute? It's all very well heaping abuse on me, but what is your specific point? What are you disputing?

"gravity is responsible for pulling the arm backward"

Also, that is a wholly accurate statement. If pedantry's your game, you need to be more careful about what you claim to be inaccurate. Remove gravity from the equations and you remove the backward pull. Therefore gravity is indeed responsible.

Now can we move onto something of some actual value?

Final post (really :D):

Its good that I addressed the technical details in the previous post to all but you. A lengthy argument against this precisely has yet against fallen on deaf ears. This is getting quite laughable now. I argue against "gravity being responsible for pulling the arm backwards" and you say I constructed a strawman and in the same post repeat the so called "strawman"!!

Lets leave it at that. So yes, I have nothing useful to contribute, nothing that will be useful to you since you choose not to listen/read.

Gravity IS responsible! Did you ever study the nature of cause and effect, or logic? Remove gravity and you remove the pull. Gravity causes the cause- making it a cause in itself.

Tell me- when you kick a football, is it "wrong" to say that your foot was responsible for moving that ball- rather than detail the complex chain of reactions that moved it?

Anyway, seeing as you started this relentless attack on me, please either make a criticism with PRACTICAL consequences that are worthy of discussion, or stop this tediously irrelevant onslaught.

No. Remove gravity and you remove the pull, not its direction.

Sorry I lied about the previous post being my last but I cannot believe how much senselessness is being projected here!

I gave you specific mechanisms by which you DON'T remove the pull just by removing gravity. I described a practical illustration of it where the gravitational force (weight) is exactly the same in two situations but changing the angle of finger (and thereby the direction of the muscular forces acting on the key) changes the pull. I have done logic, I wonder if you have.

A does B
Remove A, B disappears.
So A must cause B.

is fine as long as the second statement is true. I argued against it. You termed it a strawman, yet you use it in your "logic". Quit trying to fool people. If you want to call something a strawman, make sure you know what a strawman is in the first place. *sigh*.

N., I'm finally understanding what you've been talking about. It just came to me. Somehow the visual of the chain didn't do it for me.

So I thought about a hanging rope/wood bridge vs. a steel bridge connecting across two cliffs.

The hanging bridge pulls on it's attachment point at each end. Easy enough to understand logically without scientific references.

If the bridge is stiff as a steel bridge with all the supports allowing it to retain its structure, then the only force at the ends is down. There will be no pulling motion.

That's also easy enough to visualize.

Transferring this thinking to what you are saying, if you stiffen the arm, it becomes a steel bridge and the force will be primarily down on the fingers.

If you relax all the muscles between the shoulder and the fingers, then it's more of a hanging bridge and a pulling force will be felt.

Now understanding this does not make it clear how other techniques are wrong since I'm not aware of anyone advocating stiff elbows/arms etc.

But at least I'm on board with your starting point. From a beginner's point of view though, it seems apparent from this imagery that stiff arms translate to more downward force on the fingers. Overdoing it makes for a harsh sound.

On other hand, stiffening the arms temporarily is often done to transfer the force down to the fingers for very loud chords. At least now I understand why stiffening the arm does that.

Perhaps you have a coherent explanation for us? There's no way I'll ever understand that verbosity (whatever happened to Occam's razor?). I don't see how if its mass hasn't changed a body's weight could.