Well....one thing for sure: Rubato is not only hard to play, but hard to talk about!
I find it a lot easier to talk about than to play, but I think that's mostly because my technique is bad. Talking about it helps me learn how to get better, though. (I have learned a great deal from PS about technique over the years.) I know what you mean about 'tempo rubato' but I think I addressed that in the longpost below which I had written before you posted again (sorry for the length...I've been distracted the past week and just got here), and it just so happens to be underneath my response to your other post. In short, what I said is that tempo=time, and rubato=stolen. Time is stolen (or borrowed), but theoretically it all adds up...because, as George said, it's a cohesive whole. With hands-together rubato, the time is stolen by one part of the piece from the other, and this is only reflected in an abstract way, if you happen to have a sense for that sort of thing. With hands-together rubato, the melodic hand steals time in one part of the phrase from another part of the phrase, or perhaps from the next phrase, and the accompaniment hands keeps on trucking because it's all going to add up anyway. In this case, it's less abstract because the accompaniment hand demonstrates the tempo - the fact that it all adds up in the end - in such a way that the listener will most likely be conscious of it.
...many people who are unable to keep a steady pulse pass it off as rubato.
Many people use it in the most difficult passages, too. You can see Ashkenazy doing this all the time
in his complete Chopin recordings. It's not because he's not technically adept - I don't think I've ever heard anyone play the b-flat minor sonata as fast as he does (not in the complete recordings, but another recording) - but because he spent almost no time on most of the pieces. To the non-pianist, it might even sound musically appropriate...but the pianist (especially the pianist who has played these pieces) knows he's cheating.
It is so dangerous to start out with playing Chopin in a so-called romantic manner, without first having learned to play in time. It seems like all beginning pianists want to play Chopin above all. I was no different but have come to see the error of my ways.
A lot of people forget that Chopin was an amateur. He never had a piano teacher. Even his most difficult pieces are 'easy' in the sense that he only wrote what came naturally to his hand. The fact that everything came naturally to him (and the fact that he liked to challenge himself) means that it's still some of the most difficult music for piano, but it's easy to see why most people start with Chopin, and why most young pianists find Bach counterintuitive in comparison.
I realize that yes, it's my right hand that I can direct more freely if I want to. And that's because it's the melody line we're talking about. But what if the melody was in the left hand? Has anyone encountered a piece of music where the left hand is supposed to play with some rubato? I doubt I could ever do that!
Sure you could, and I think you have. A good example is Chopin 25/7. A totally different but still nice example is 10/12. As I've said before, I hate that one when it's played straight...and yet, it suffers from a loss of pulse. As someone mentioned earlier, it's not as if we're talking about metronomic tempo anyway. A healthy pulse is regular, not metronomic. Without the regular pulse, then syncopations and the like lose their meaning completely, but in the operatic type of melodic (usually RH) writing that Chopin is known for, the accompaniment hand can keep the pulse and still allow much room for melodic freedom, and with that freedom, meaning is only added, rather than lost.
The most important point is that rubato is 'stolen' or 'borrowed' time. One part of the piece steals time from another - or on a smaller scale, one part of the melodic phrase steals time from another part of the phrase, so that it all adds up. Kallberg has talked some about these two types of rubato - the 'hands together' and the 'hands separate' types (in addition to the mazurka type), but generally Chopin preferred that the performer not insert ritardandos or accelerandos unless they were written in the score - the slowing down and speeding up of the hands-together rubato should never venture very far from the regular pulse. As Chopin said, it takes you more or less the same amount of time to play the piece as you would have with the metronome. If you speed up Here, then chances are he wrote the music so that it makes sense to slow down There, etc.
Someone mentioned polyrhythm earlier. I also mentioned this on Rich's nocturne thread in the AR. It's not rubato, but it can serve as an exercise in how to play hands-separate rubato because it teaches independence of the hands. Sometimes polyrhythm breaks up in simple proportions, like 2 against 3, and therefore the pianist generally learns to think of it as an exact science. 3 against 4 is a little bit tricker, and so on. Eventually you have to learn to think by the larger beat that encompasses both sets, and play each hand independently against that beat. I like the TN F minor nocturne for this because rubato is appropriate in it. Chris might say that's because I like to cheat...but I can do 3 against 4 exact. I don't think that is what Chopin is trying to teach people with this etude. I think he is trying to teach people how to play his music the way he played it. If it's contrived, it's not going to be good, but maybe if we make the attempt it will get easier for us as time goes on.
I had this conversation with Alfie in email some time ago, and he provided some recordings of Mikuli's students to demonstrate that this 'school' of piano playing is extinct (as if to say, 'if it ever existed'). In a way, I see what he was getting at - playing with discipline and freedom at the same time is immensely difficult, and I really doubt Mikuli was any good at it. Most agree that Princess Czartoryska and some of the other talented females were most true to their master's style, along with Karl Flitsch (who unfortunately didn't last long). So why should Mikuli's students have carried on the tradition? As was demonstrated in the Chopin etudes thread on the Repertoire forum (?) pianists tend to see piano technique in this way, as a school of thought that must be passed down from teacher to student...but in practice that's probably an unproductive way of looking at it. All of us who play Chopin are students of Chopin. No one living can tell us how he played, and the accounts from the past are only useful to an extent.
Rendering any "Musical dissociative disorder" seems a bit stretched, because deviations relating tempo or synchronicity is intentional on part of the pianist, and it is not involuntary, nor pathologic. It's a matter of taste. Synchronicity is mathematical and absolute in written manuscript, but any tempo deviations via rubato really should involve BOTH hands, and not just one hand.
This, I disagree with, mostly because I think the pulse is often broken by this type of rubato. I think people use it often because it is by and far the easiest way to execute rubato in Chopin's music, and Chopin's music sounds awful without it (even the most mechanical of the etudes). But I also think that Chopin's music suffers from a loss of pulse, if not so much as from a lack of rubato.
Music is cohesive, not dissociative.
In general, this is true, but that doesn't meant that dissociative elements cannot be effective within the cohesive whole. Undoubtedly, it depends on the talent and skill of the interpreter...and that of the composer, of course.
The golden age of Romantic pianists would do this kind of thing more often. But the argument is passe as tastes and conventions have changed over a 100 years. However, these days, regardless of the temptations to stray from what is written, "dissociating" or dis-synchronous playing is the trait of an amateur and not correct in almost all cases.
If the music suffers from an amateur class performance, then it's probably not best to judge the value of this type of rubato from this type of performance. By all accounts, Chopin was unparalleled in his pianism, though some criticized his amateurish approach. Notably Czerny.
Later in his life, when he wished he could make a living as a concert pianist, he only half-regretted his refusal to make a machine out of himself in his youth in order to pull it off. Probably not even half.
One thing that I do too often, and that many do too often, is the delay of the RH note when it's obviously intended to be in sync with the LH, such as on a downbeat or another strong beat. Chopin hated that, not because it's never appropriate, but because it's so easy for we, the amateurs, to overuse it. When we overuse the expressive device, it loses its meaning. I have a tendency to do this more when 1) I'm tired/distracted/stressed, or 2) I'm playing the piece faster than I should, and therefore my grip on the piece is less secure.
In conclusion...it's easy to see why Brendel said that Chopin requires specialization more than any other composer. It's not that the technique requires specialization, exactly. The interpretation requires specialization. Brendel knew that, and he chose to give up on Chopin, probably not because he didn't get into it, but because he had the choice of 1) playing nothing but Chopin all the time, or 2) playing other stuff.