Interesting, the Schubert Op. 90 #2 Impromptu was one of my core pieces in my First Repertoire. (The entire rep was wiped out when I had no piano for 6 months due to family crisis.)
YOUR MEMORY LEVEL?You didn't mention your memorizing ability. Is it the least of your problems? For me it is 90% of my problems. Classical and Baroque are very easy to memorize but can be a bear to play. In particular, Pires doing the Shu Op90 #1 is so heart wrenchingly sad, it literally brought tears to my eyes.
PIRES: PLAY #1 as #10:You MUST check out Pires' on stage ready to perform a Mozart concerto.... and the orchestra starts playing the
wrong one! Since then I am a diehard Pires fan. And listening to her #1 confirms her genius.
Which leads to the point of playing a #1 grade at a #10 level. The simplicity of the Shu #1 is trivial, but
each note has it's own story. What is nifty about a piece like that is if you can get it right, you will have anyone, anywhere eating out of the palm of your hand. Further, I would say if you play below your level, find stuff like that. Lots of pianissimo and rubato - perhaps focus on that for these types.
MODERN COMPLEX MUSIC:Which leads to the Other Types: Difficult technically and complex making memorization difficult. It starts around Chopin and progresses to Rachmaninoff with Liszt wreaking havoc in the meantime. Then if you head way out there, you get into Prokofiev, Stravinsky, Ravel, and eventually Ligeti. That stuff is so wicked hard to play, understand (I'm joking right?), and lastly memorize. In fact, a consensus is brewing about memorizing in general. With the complex
avant garde that is out there, memorizing beasts like Yuja Wang uses music. Martha seems to be using more in her Old Ag3, but then she's Martha, and what Martha wants to do, Martha does - and we love her all the more. (If you want to curse someone about memorizing, it appears Clara Schumann was the culprit as was Chopin for the recital. I curse them both in that regard! BTW, only Violinists and Pianists are expected to memorize.
WHAT I'M DOING:Which leads to what I'm doing: the exploration of modern complex music with my limited mental processing power. Since it takes me forever to memorize something complex (Prok's Precipitato is over a year old for me and still my recall is "dropping frames"), I've throw caution to he wind and am embracing pieces that I'm crushing on. The Prec was one - I memorized it in maybe 6 weeks which for me was record breaking, but it was an obsession. Rach Etude-Tableaux #6 and Prok Toccata are massively difficult, and it will take years to get them anywhere playable, but then, that suits me fine. The way I look at it, if I could play the Toccata, just that one piece, I would be content.
ACCURACY, SPEED, and EMOTION: (
NOT in that order!)
I used to be obsessed with accuracy. This is the least important of the three. Emotion is #1 and so is speed because if you slow down, say Gershwin's Preludes to get he notes right, that is an epic fail. You can practice accuracy and try to bring accurate speed along, but when you perform, you have to play it the way it must be, speed and emotion wise.
Remember what Beethoven said, Beethoven who some used the adjective "demonic" for his performances - and yes, he probably was playing with sheet music (!) (I think Liszt was one of the first virtuosos that memorized.)
Beethoven said to a student: (
It ain't the meat, it's the motion.)

"In the Variations dedicated to the Princess Odescalchi (Op. 34), I was obliged to repeat the last Adagio variations almost entirely seventeen times; yet he was still dissatisfied with the expression of the little cadenza, although I thought I played it as well as he. On this day I had a lesson which lasted nearly two hours. If I made a mistake in passages or missed notes and leaps which he frequently wanted emphasized he seldom said anything; but if I was faulty in expression, in crescendos, etc., or in the character of the music, he grew angry because, as he said, the former was accidental while the latter disclosed lack of knowledge, feeling, or attentiveness. The former slips very frequently happened to him even when he was playing in public" (TF: 295; --