As a piano student, fingerings are possibly one of the things I've struggled most with. When I first started having lessons, the simple fingering patterns for playing scales in both hands completely confused my brain. I got used to it pretty quickly, and it soon became intuitive. Nevertheless, fingerings remain the problem I most often need to consult my piano teacher about, and they are a source of minor disagreement between us.
I started having lessons relatively late, at the grand old age of 11. Before that, I had taught myself to play, and learnt or attempted to learn some quite complicated pieces. As a result of having no guidance I developed a few 'bad' habits in my technique. Some of these habits disappeared once I started having lessons, but one persisted for some time (and continues to persist even now, in a way). This was my unconventional choice of fingerings - not in scales but in actual pieces (I usually stuck to the textbook version of things for scales.)
I firmly believe that since everyone's physical shape is different, there can be no RIGHT fingering for a certain passage. I rarely find the 'official' fingerings printed in scores, if there are
any, satisfactory without at least some tweaking for my individual
comfort. What feels quite natural to someone with large hands and long fingers, for instance, might be impossible for someone with smaller hands, and that person might find it easier to use a fingering which the person with larger hands finds very clumsy and awkward.
However, there seem to be certain conventions in modern piano playing
that state that some fingerings, in some situations, are
simply...forbidden. Illegal. 'You can't do that. It's not an approved
fingering.' That's the feeling I get, anyway.
In any case, my teacher and I usually disagree about what fingering
is the 'most natural'. The fact is, there is no absolute 'most natural'
fingering because what is natural for one person's hand shape can be
extremely uncomfortable for another's. This is actually the scenario that crops up quite often with my teacher these days: he has huge hands (able to span an eleventh) while I can only span a tenth, which is quite a big difference even if it only amounts to one note on the keyboard.
However, one of the reasons I like to consult my teacher about fingerings is that often he DOES come up with a much simpler and more natural solution, which, for some reason, I would NEVER have thought of myself. I have a strange tendency to devise fingerings which are unnecessarily complicated. Often I will write a
fingering onto a score which felt quite natural at the time, only to go
back to it later and wonder 'why on earth did I do that?!' The fingering I find 'most natural' at a particular time for a particular passage I've learnt may feel completely wrong in a years time when I go back to that piece and try to play it again. This is especially the case in Bach.
Bach is not pianistic music. It was written in a time when pianos as we know them today didn't exist, and where keyboard technique was far removed from the flowing, velvety legato that came into existence in the Romantic era. The fingerings in Bach are atrociously awkward, and more or less defy everything that the Approved Textbook of Fingerings tries to tell you (I just made that up, by the way...)
Very early on in my piano education, I half-learnt the first movement of Bach's 2nd partita. Despite having very little knowledge of the conventions of piano technique at that point, I actually learnt to play it at a considerable speed SOLELY because I used 'illegal' fingerings. At that point, I hadn't learnt any of the conventions of fingering, so it didn't feel unnatural or even awkward to break the rules. But today, as a pianist who plays Chopin and Rachmaninov and can hardly approach a black note without using the 4th finger on it, when I return to that partita it just feels...wrong. I can't play it at all anymore. The fingerings are too unnatural compared to the 19th-century Romantic technique that has become intuitive to me.
That's not to say that I have COMPLETELY dropped my unconventional fingerings - quite the contrary. I'm now learning Bach's D Minor Concerto, and while my fingerings might not be as outrageous as they were when I learnt the partita all those years ago, they still spark a lot of controversy during lessons!
I would be really interested to know what other pianists/ piano teachers thing about 'illegal' fingerings. Are there any fingerings you wouldn't let a student use, and if so, how can you justify it, since you can't BE them and experience what it's like to play a particular passage with their fingers?