When playing piano on a piano bank I feel really comfortable but when I write at the computer using my old revolving chair I very quickly get tense in my back, shoulders, arms and hands, probably because it doesn't go as high as I would like. Seeing that a piano bank can be had for much less than a good new chair and that such a bank guarantees an upright posture it seems a better alternative to me, especially as there seem to be many old piano players in great health. Am I right in this estimation or is there some problem I can't see about the ergonomics of long term piano bank use for the computer?
First, congrats on actually being more comfortable sitting up-right. I've yet to master the talent.
In short, I can't say the relation between old piano players in great health is directly related to or, is the result of a piano bank and an upright posture.
That being said, a majority of the money spent on office chairs are for those ergonomic adjustable features for lazy sitters (myself included). If I can buy a chair that will posture me for me, count me in.
Now, a backed chair I'm sure was purposed to keep people from falling off the back end but for today's office oriented purpose of keeping you upright, you're able to do without.
Use whatever makes you comfortable and doesn't pull you out of the correct posture.
Just out of curiosity though, does your as* ever start to hurt? That's the only concern I see from using a piano bank at my desk!