Yes, it was misleading colomon, I was referring to the piano as a whole, not just the C scale.
That’s a good link. Reading the whole thing…along towards the bottom, it verifies what I was saying about a “just” piano sounding off. It’s talking about why an organ isn’t tuned to “just.” And, it talks about why “just” doesn’t work for other keys in the 12 note scale. The octaves are always perfect, from one to the next, but not especially from one to the third and fourth above. As the article says, the octaves are progressively stretched (according to math and the machine), because the further the note gets from middle C, the less accurately the ear interprets the tone. A perfectly mathematically tuned C, four octaves above middle C will sound off to the natural human ear…it’s getting close to being out of our hearing range, so the strings are stretch to let the imperfect human ear think it’s in tune. There have been times when I have just stretched the upper 7-8 note out of hearing range, and no one could even tell. I only do that on painos with terrible sounding boards that offer false harmonics.
I’m not sure how to explain it any further, but if you set the temperment scale F to F, around middle C, and tune it imperfectly to itself (called the temerament scale), then all octaves perfectly to each other (involving the progressive stretch, both up and down) you have a perfectly professionally tuned piano that is tempered, or tolerably imperfect. Make any sense?
A paino tuned “just” is just wrong, as discovered by Bach, although the octaves are the same, except there’s no stretch (mathematically speaking) in “just.” and any instrument tuned to “just” can probably be played with the piano (tolerably) in the middle octave, but when it goes to the second, you’ll not like it. Just would be right if we played in one key the human ear was right, but it ain’t, so we compromise and call it good. And it is as good as the human ear.
Ted, our senior uilleann piper expert from the UP forum just advised pipers not to try to tune to electronic tuning instruments because the playing note, due to pressure differences, will be different than the tuning note. It’s not stable enough for the subtle differences. And, on the whistle recorder, and flute, the instrument is tuned to each person’s embouchure, not to a machine. That’s why it’s good for some and not for other. Don’t tune individual notes to a machine. Tune one note maybe, the one in the middle most easy to repeat, then tune the rest of the whistle to that note while playing to a drone or other stable instrument. You’ll see pipers and flute players taping holes, filing, filling with clay or putty, it has to be individualized.
Hands-on experience with piano tuning will teach anyone that there’s almost an imperceptible difference between a tempered and just 4th (C-F) and 5th (C-G), but it will show up in the 6ths (C-A) and 3rds (C-E)…the tests for the piano tuner.
You’re right Jerry, it’s not out of tune with the piano or each other, at least to the imperfect human ear which we all nearly have. Just is always out of tune with tempered, technically, but I would challenge anyone to demonstrate the difference, hitting the two different notes in succession by voice, or with a bagpipe, etc, with the listener looking at his $5K tuning machine, lights rotating each way in thousandths p/second. 
Erik, a life of concern for details made me that way!
Now I have an adversion to generalities. BTW, we just had an lady move down here from Alaska. She organized Irish music concerts, dances, etc., and played with a band. Her name is Laura Hall..do you know her?