Hi Alex,
Normally, when we talk about "voicing chords", the concept pertains to the RH. I'll start there and get to the LH in a moment. In many pieces, a student might gaze at the chords in the RH, and the visual impression is that chords are vertical groupings of notes. But very often, chords in the RH must be considered not vertically, but horizontally. The reason is that those chords have a melodic line running from one chord to the next and the one thereafter, etc. Typically the voice line is in the "tops" of the chords, but sometimes there can be a hidden line in a middle voice of the chords. Once in a while it is appropriate, given performance practices, to voice the bottoms of the chords.
The voicing I refer to in the Prelude No. 4 occurs in the LH. The reason I gave an explanation of RH voicing first, is that it is more prevalent for projecting melody. The reason for voicing changes in the LH of this particular prelude is different. Rather than being melodic in nature, these are important harmonic changes that add color. As such, they help maintain listener interest in what could otherwise be a dull and dreary ostinato type of accompaniment. There is an old saying of composers: "Always keep the bass moving!" Chopin was a master at this. The purpose of that is to enhance musical value and to keep the listener from becoming inattentive or even bored. That's why you need to highlight these harmonic changes. You must do it sufficiently, but not in an exaggerated unmusical sense.
The word "voicing" is appropriate to the pianist's purpose. Music is all about voices. Instruments--the piano, violin, French horn, etc. are just that--mere instruments. They are there at the musician's disposal to imitate the human voice. So, for example, when you have a soaring catilena melodic line, you need to be singing it in your head as you voice or etch the melody to best approximate how it would sound in song. Voicing requires emphasizing certain notes with fingers, arm weight, and/or sometimes the positioning of the hand. It is a learned technique that takes time to develop.
Analysis of a score can be learned in several ways. For a pianist it generally occurs during years of piano lessons. An artist-teacher will point out, for example, matters of form and structure in a Bach Fugue, or for a sonata. There will also be teaching moments for voicing, phrasing, overcoming a technical hurdle, improving tone production, employing portato touch within in a certain phrase, using half or flutter pedals, etc. etc. The student absorbs these and many other lessons over time. The artist-teacher has only one goal really--to teach the student how to be his or her own teacher in the future. Another way to begin to analyze and interpret is by reading books on piano performance and pedagogy. It helps too to accompany singers to see how they phrase and breathe.
So when I get ready to study a new piece, I do not sit at the piano initially. Instead, I sit in a chair with the score and study it. First, I'll look at the key signature, meter and tempo as well as the larger form. Perhaps it is a piece in A-B-A form. Or there might be a reprise in the theme, or a coda deserving special attention. I highlight dynamics, changes in touch, work out logical fingerings in passagework, finger transfers, notice voice leadings where a note in the RH, for example, points to the next note in the LH. I might find an odd rhythm that I'll pause to figure out. Perhaps I'll see a really difficult short cadenza, and I'll be thinking of intelligent ways to practice it other than pure repetition. Looking at the texture of the piece will be important to form preliminary ideas about pedaling. I'm always on the lookout for voicing requirements in both hands. When touch changes from legato to portato to nonlegato to staccato, I note it. And yes, ha-ha, if I encounter an unfamiliar musical term, then I'll look it up in a musical terms dictionary and note it in the score. I also find it helpful to consult books about the composer that reference his works. Repertoire guides also briefly discuss the character of a piece sometimes. Or you might find that a pianist studied a piece with the composer who wrote it and discusses the composer's intent in a book or article as it was told to him. Or sometimes your teacher's teacher studied with the composer. Many performance practices have been handed down by teacher to teacher to teacher through the generations.
On interpretation in learning a piece, I try to stay clear of recordings. I want to make my own determinations in that regard and put my own stamp on a piece. Once the piece is learned, then I might listen to a recording later to compare. But usually, it is to see if I've overlooked a wrong note. Once in a while I hear one and recheck the score. But as often as not, I'm correct. In that regard, different editions can account for these apparent "errors". Thus, both pianists and be right. Using urtext editions that are as close as possible to the original is helpful, especially if the editor or editorial board has a comments section to discuss details.
I have to admit that I'm very unfamiliar with digital pianos. So if you have a soft pedal there, use it to good advantage when you must play very softly.
Hopefully, this explanation is helpful.
David
Topic: Prelude Op. 28 no.4 -Chopin