a base question, will appreciate any suggestions.

[huaidongxi]

forty years ago as a brute youth with only rudimentary training in technique, could go at the keyboard a couple hours with vigor and not have any physical issues.  Presently, attempting to rebuild a better foundation after a long absence from practice, and intervening physical labour, bike riding (never owned a car), tennis, plus age, plus a likely inherited susceptibility to arthritis have frayed most of my tendons in many joints, the right thumb, fingers, wrist noticeably.

It's a requisite then to minimize stress on the old joints and tendons.  Observing high level pianists, though, it looks like there is no single ideal sitting height for everyone.  From what I can see, many or most practitioners are at a level where the relative hand (at keyboard level) and elbow elevations are close to neutral.  Smaller players though sometimes appear to be sitting a bit lower when they have adjustable benches (never had one myself), so their wrists and hands appear to be slightly elevated relative to their elbows when the fingers are on the keys.  This appears to be the case as well for the inimitable Alicia de Larrocha, one of the few supreme artists with small hands, and therefore a possible role model for me [my span is barely a tenth, less depending on the specific note combination, and four note chords with the outer notes separated by a tenth or eleventh, not uncommon in the literature, just won't happen].  my height is exactly average for a u.s.a. male, my arms are on the short end of normal for my shirt size and shoulder width (about 40 in. circumference by conventional shirt/suit measurement).

Are my observations mistaken, or not, and if not, what seat height is less stressful biomechanically in theory ?  thanks in advance to all the experienced instructors and practitioners who share their wisdom here.

[thirtytwo2020]

You are correct in your observation that many pianists try to keep their hand and elbow more or less level. This is a common recommendation.

However, as you point out, there are exceptions, and I think it would be hard to claim with certainty that sitting on a slighty lower or higher level than normal would in itself be biomechanically stressful. The most important things are of course to be able to play without unnecessary tension and to rest frequently. I don't think that there is any obvious connections between how big a player is, and the hand-elbow relative position.

I would strongly recommend that you buy an adjustable bench, to be able to find your own ideal sitting height more easily!

[adodd81802]

I don't think you can look at a pianists hands as an idea.

Everything is different, I can only reach a 9th, and 10th around the keys, i'm 5ft 10, 34inch waist and quite a broad guy, top heavy.

For me I prefer sitting just slighly higher than the keyboard, my elbows probably still drop in between the white key area, but I find for fast runs and arpeggios I have much better form being just above the keys I don't feel like i'm lifting my hands with as much effort as if I was in line or slightly lower.

Check out Glenn Gould for one extreme, showing that arguably, it doesn't matter as long as you find something that's perfectly comfortable for you.

As advised an adjustable bench is a suggestion, maybe start in line with the piano for a week or two, see how you go, if you feel any discomfort, consider higher or lower options and progress from there.

You are too low if you feel like you're raising your shoulders or that your arm becomes a slide to the elbow and you're too high if your wrist arcs between your arm and hand causing a slope.

[dcstudio]

actually it's not good to condition yourself to one position... that will cause you pain more quickly than anything.   I am 51 and lately I find that in order to put in the hours I need to I have to spend time playing with the bench in different places and my arms extended to different degrees.   In doing so--I have found that moving farther back from the piano with my arms extended solves a lot of my back and neck issues and really gives me way more control.    I am a totally obsessive player and I have been for decades but I still have posture issues sometimes... it really sucks when you get spasms in your back and you have 30 minutes left to play before your break.  I also try to exercise my stomach and back muscles to minimize this--pianists are not known for their obsession with physical fitness..  so that's a struggle in itself.

[xdjuicebox]

Dang I wish I could reach an 11th haha. My hands are average size, but I can barely reach a 10th, and I have to strain a lot to do it (working on that flexibility!)

Anyway, bench height is actually a very controversial subject; but both positions have its advantages and disadvantages. A low bench height allows you to use your back muscles in your playing (like Vladimir Horowitz and his low wrist positions where he pulls down on the keys, [https://www.youtube.com/watch?v=OfeNR-2L51s], but then again Vladimir Horowitz barely practiced, and that might have been because everything was hurting...), and a high wrist position makes it easier to use gravity better (at least in my experience). I've played on a lot of adjustable chairs, so I'm constantly adjusting my technique based on the circumstance (which probably isn't a good thing), but that's what I've found.

The most important thing, however, is that your spine doesn't go out of alignment, because if your back/neck muscles have to work harder to keep you upright, it bleeds a lot of energy from your arms

[indianajo]

I was taught the hand is supposed to be a bit lower than the elbow, with the wrists straight, and the fingers curved naturally, not flat.  
It turns out that position is recommended by ergonomics textbooks for typing injury free, also.  Ergonomics is the study of movement in industry and commerce.  
Ergonomics texts also teach the head should be able to look straight ahead at any material being read as well as typed.  
The drooping forearm position is not that hard to achieve with phonebooks or bricks under the bench.  Pianos do not have adjustable arms like typing print holders, so getting the head position and sightline right is a bit of a trick sometimes.  I'm short, which make proper position pretty easy.  I'm 65, have typed a lot in industry in addition to piano, and have very litte pain in the tendons.
BTW, organists use flatter hand position, but with electric action, not much force is required.  I don't know anybody that plays on trackers (wood slide keyboard organs) to see how they do it.  
Horowitz with his infamous low flat hand position, paid for special low force pianos to be made or modified and those pianos toured with him in a crate at great expense, so see where that hand position will get you.  
I'm playing a lot of tenths in my current practice piece, so if that was going to cause a problem it should show up by now.  Tenth is my max on white keys and a little less if one is black.  
One final word. My mother's neck disk was popped by working one day typing with the incorrect table height and head position.  No amount of surgery was ever able to repair it. She was in pain every minute of the rest of her life. Sit right, or take up television watchng in a barcalounger as a hobby. 

[huaidongxi]

appreciate the time everyone spent considering my request and emphatic thanks to those who extended a response, all of it is quite helpful. reviewed what Thomas Mark ("What Every Pianist Needs to Know about the Body") had to say, not that he is more legitimate than the folks here who've spent tens of thousands of hours at their keyboards.  he essentially confirms indianajo's view.  [der kapellmeister van indiana is also around my age, and two of my favorites, Tatum and Monk, grew from the roots of stride piano].  Marks rationalized how players are successful and injury free with differing seat heights, stating the key was keeping tension free, the point made by nearly everyone.  personally, would take neither horowitz nor gould as role models, listening to their performances is of course a different matter completely.

may you all enjoy relaxing and rewarding hours at your instruments. peace.

[dcstudio]

appreciate the time everyone spent considering my request and emphatic thanks to those who extended a response, all of it is quite helpful. reviewed what Thomas Mark ("What Every Pianist Needs to Know about the Body") had to say, not that he is more legitimate than the folks here who've spent tens of thousands of hours at their keyboards.  he essentially confirms indianajo's view.  [der kapellmeister van indiana is also around my age, and two of my favorites, Tatum and Monk, grew from the roots of stride piano].  Marks rationalized how players are successful and injury free with differing seat heights, stating the key was keeping tension free, the point made by nearly everyone.  personally, would take neither horowitz nor gould as role models, listening to their performances is of course a different matter completely.

may you all enjoy relaxing and rewarding hours at your instruments. peace.

monk and tatum?  can't say that I hold a candle to either of them but you and I are going to get along fine.