AJ, you're so helpful to all of us. Thanks. I still need to take a look at the notes you posted on my topic.
Honestly its not a selfless thing. I'm no expert and trying analyze and solve a technical problem does a lot for me as a pianist and teacher. And none of my current students are going to bring me tough questions about advanced repertoire so it's a lot of fun for me to do this.
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I worked on bar 55 last night for a short time, I will detail my problems which seem to be in line with yours. I was able to solve them and play fluently from 54 to bar 56 at a moderate tempo, no where near final speed though. I didn't bother dealing with the rest since that was not your question. I can also deal with the triplets fine but I won't touch on that here because you'll end up with an 5000 word essay to read.
Ok, step 1. - playing the right hand chord accurately and quickly.
My initial tendency was to miss the top D, and sometimes the A. So, fix - just had to play it 20 or so times by it self with the relevant movement which for me was as follows. The bottom A has to e played with a rotation toward the thumb, this prepares you to roate back the other direction for the other notes. The rotation at the top of the chord was fairly extreme, as I come off the high D my palm is facing to the left rather than down toward the keys. Doing it this way helps with 2 things, firstly you will not be inclined to 'hold' the lower notes of the chord which would mean a tense stretched hand, by using the rotation your had can remain relaxed for the whole chord and your wrist can stay aligned with your arm, avoiding the left/right and up/down wrist motions here will keep you balanced. Additionally, being in this position at the end (palm facing left) means that you can perform a fast accurate rotation back toward the thumb to play the next chord. If your getting it right this is a naturally fast motion, you will likely be able to play the RH faster than final speed and with great power.
Step 2 -
Practice just the rolled chord with the bottom B in the left hand only, so that you can get to focus on the RH while playing the left hand aswell.
Step 3 -
Add the last F# from bar 54, so now your LH plays that single note followed by HT b and rolled chord
Step 4 -
now don't worry about the F#, but use the same concept going the the other direction. You will play the low b with the rolled chord followed by the next LH b an octave above the first. You can watch you RH as you play the chord then watch you left hand as it comes over for the next note. As it gets more solid add the other left had notes from beat 1-2 of bar 55, but not the RH second chord yet. Focus on getting a sense of 'finishing down' on the rolled chord ad low B before you continue the LH. This may disrupt your tempo but as you speed up it will sound more like an accent/rubato than a lack of continuality.
Step 5 -
Add in the next RH chord, when this is comfortable I want you to cycle it, that means play beats 1-2 of bar 55 in a continuous loop until your are getting it in time an accurate almost always.
Step 6 -
Now play from bar 54. This time you are working not on the note of bar 55 but on the getting to bar 55. As you come in to bar 55 remember to focus on getting the first low B and rolled chord played before you worry about the next notes. If you don't do this you can become so focused on the following notes that you are tryin to move to them before you play the first note. This could be a reason for missin the top D, in that we may have a tendency to play a b or c at the top of the chord because we are already trying to move in the opposite direction to get back to the second chord.
Finally you may then need to do some isolated practice of the transition between bar 55 beats 1-2 to 3-4
I don't know how long it will take you to perfect but this took me about 10-15 minutes, long enough for my gf to have a shower actually, I'm just assuming that was 10-15 mins. This is the exact process I used, you may need to focus on one aspect more than another. Be consciously aware of exactly where your problem lies by testing all these different ways of playing the notes surround this or any other problem, then you can practice the actual problem instead of all the other mess around it..
I'm sorry I can provide a video for the technique of the rolled chord, I will try and scour YouTube for something later and if not try to do something myself when I get enough spare time to do the 85 takes it will likely require for me to be satisfied with a video.
Let me know how you go.
AJ