Hi Rojo,
I guess in keeping with the thread's title, I have done some vexing! Sorry about that. I guess it's my own vexation taking itself out on the wrong person. I've played too many times with instrumentalists who drove me crazy about tuning, but no, it's wrong to make blanket statements.
Let me see if I can fix this.
I do, really and honestly, believe all musicians should be taught at least the principle behind tempering a keyboard and maybe even to sit down and do it. The reason is that a true understanding of temperament would help a choir, for instance, deal with the wandering pitch problem when they sing a capella, and would help string players keep their pitch when playing quartets or other pieces with strings alone. I don't mean this unkindly, I mean that I believe it is a failing in modern music teaching. Once equal temperament became more or less standard, musicians did not learn so much about this.
Ok, let me explain. One would think, all things being equal, that we would prefer to hear IN TUNE intervals. And I remember all my years as a trumpet player (8 years) of people talking about this mysterious "in tune" thing. As far as I could tell, the piano was "in tune" and that was what we were supposed to sound like.
It was only later, when I began to learn about early keyboard technique, that I learned the intervals on the piano are not in tune, none of them. What we have nowadays are a lot of confused musicians who never really know what real in tune fifths and thirds sound like. Now string players are more sophisticated than other musicians when it comes to this, and I will say that very advanced strings players DO know about tempering. Some string players temper the fifths on their strings when they are tuning. What does this mean? You tune a purely in tune fifth, and then you make it ever so slightly out of tune.
I am not saying that keyboard players are "better" or something like that. What I'm saying is that some of us confront this issue more than most other musicians, and that is those of us who play the harpsichord and have to tune all the time. Pianists do not, and they tend to be the most ignorant of all musicians when it comes to temperament. They call the piano tuner, he tunes it, and it's "in tune." Wrong. It's OUT of tune if equal temperament is used, actually more or less out of tune no matter which system is used. Many of us, especially harpsichordists, prefer older tuning systems because at least SOME of the intervals are in tune, whereas in equal, they are all out, thirds more than fifths. Keep in mind that it's a misunderstanding that Bach promoted equal temperament with the Well Tempered Clavier. The evidence is that while the idea of equal temperament was known, Bach specifically avoided it. Well tempered and equal tempered are two different things.
String players have the most trouble when they play with a piano or an organ, because they like "just" intonation, where there are in tune intervals. The unfortunate thing is that on occasion I've played with good string players who were not advanced enough to understand tempering systems and they complained constantly and blamed me for not having the instrument in tune. If they actually knew what they were talking about, they'd have understood the problem. This is why I say ALL musicians really should understand keyboard tempering.
I also say this for choir singers and string players who play in string only pieces because once a musician has learned to hear a TRULY in tune fifth and/or third, then they prefer to use them all the time. What happens then? The pitch of the piece actually RISES rather than falls. Falling pitch comes from singers who are not supporting their tone, but rising pitch comes from singers who are acutely aware of tuning, but not educated enough about it to know when to sing OUT OF TUNE ON PURPOSE.
If you're playing in an orchestra, it tends to be less of a problem because the woodwinds and brass automatically keep the pitch from wandering. They cannot adjust pitch as much as a singer or string player, and their instruments anchor the pitch, keeping the string players from wandering.
String players who do quartet playing become very aware of these issues and they become very good at negotiating temperament. I've heard some quartet playing that set my teeth on edge, but mostly I like it a lot because of the awareness of tuning and temperament. I've heard some recordings of quartet playing that were gorgeous in their awareness of tuning issues. (And that means NOT in tune ALL the time.) But I would venture to say that any of these players at least know the theory of how to tune a keyboard, and very likely could do it.
I have actually heard of string players setting electronic tuners on their music stands to help them keep their pitch during performances. Interestingly, these tuners are NOT set to equal temperament, but Kirnberger, from what I've heard. While I find that interesting, I also feel it's a horrendous statement about their training. It is not all that difficult to learn the basics of this. I'm not special as a musician, I just took the time to learn some of the theory involved and how to do it. It didn't even take that long.