The problem with slow practice is that the behavior which it cultivates is in no way similiar to the whole-body thechnique required to play, for example, the Chopin Op. 10 no.1. So, in most cases of the fast works of Chopin, performance speed is definitely NOT slow playing which is merely "sped up". Yes, notes can be learned this way, but, particularyly on widely-spaced arpeggios, it truly is frustrating, counter-productive, and, in the end, "bears no fruit". The whole rhythmic dynamic force of the piece is "squelched".
Additionally, playing a fast piece at slow tempo makes it far too difficult to "link up" and easily recognize the notes of the melody - the thing the piece is really all about.
Far better at first to play at tempo, but ONLY the notes which are essential to recognize the melody. In the case of Chopin this may be only be one note per measure, or even fewer. So play only those notes which would allow a listener, and the player, to say "Yeah ....... I recognize that piece!" As much as we notice, and want to "say", those blisteringly fast little notes, their importance is almost nil to those few, comparatively-infrequent little notes which have elevated the works of Chopin to the highest pedestal. And it is only the player's awareness and TRUE APPRECIATION of this fact that allows him to learn those works. How ironic.
So, get the overall rhythmic and melodic idea of the piece AS A WHOLE well established in as much an outlined or "skeletonized" fashion as possible - at tempo. Using this method, one will very quickly get that feeling of accomplishment and confidence - one actually feels as if one already "knows" the piece - and, in fact, this is really close to the truth. Very soon thereafter ideas on how to fill in the embellishing notes just simply spring forth. But go back frequently and repeat that initial skeleton - it's the "glue" that holds the whole thing together, and it's the "thing" that's going to allow consistent, reliable performance.
A warning! Once the skeleton is learned, don't now decide that you're going to be the one person on the planet to play the Chopin Etudes at "double tempo"! This is an almost-irresistable tendency, and it has to be resisted at all cost. Decide up front how fast you'd like to perform the piece, and then STICK TO IT - at least until all the notes have been reliablly filled in. Then, the sky's the limit - go for it!
After learning the skeleton and then starting to focus on filling in some additional notes, don't be afraid try every motion, position, or gesticulation with whatever body part that comes to mind, no matter how ridiculous it may seem. The more of the body invloved, the better! If it doesn't accomplish almost immediately the desired result, ALWAYS WITHIN THE CHOSEN RYTHMIC FRAMEWORK, then reject it and try something else. Here, falilure is a blessing because the relative merits of each attempt are remarkably well-remembered. Each new attempt spurs new ideas based upon combinations and variations of the previous attempts. When the "correct" technique is stumbled upon, it is a real bolt of lightning that one never forgets. THAT"S IT! - you'll almost shout.
As I am learning to play these works I am always thinking that it is not my fingers which are doing the playing - it is my whole body, and that, almost invariably, a large group of keys is going to have to be "struck" in a single "landing" of the hand- played almost as a single note - and very-sensitively felt that way by the fingers they make their impacts. The fingers' feel of the "texture" or "roughness" of the landing is a very valuable tool for the player.
During performance at tempo, it never ceases to amaze me how automatic the whole affair is as long as the rhythmic dance is "running the show". It's a dance where only I'm doing all the moving and the piano is, as always, just sitting there. My whole body is so active (my arms, in particular getting into some almost unbelievable positions as they "shoot" may hands onto my "partner"), that if someone were to restrain any part of it, the whole performance would simply collapse.
To sum up, it is remarkable (and quite ironic) that speed technique is completely inappropriate for slow passages, and slow technique is completely inappropriate for speed play. To play Chopin, one has to be familar not only with these extremes, but the continuous spectrum of technique, and every step of it requires the entire body to be fully, rhythmically involved.
Topic: Ultra-fast arpeggios (ARGERICH)!!!