Well, it is actually pretty hard to explain, but I'll give it a try! My teacher studied at the Moscow Conservatory for 10 yrs under a student of Gilels and his experiences there are really mind boggling. In his entrance recital, his to be teacher came up to the piano while he was playing and looked curiously. After the performance was over, which, my teacher accepts, was not that good on accuraccy as he was probable nervous, his teacher asked something which had nothing to do with accuracy at all! She asked why the sound was somewhat thin and shallow!
Plus, my teacher didn't know the language at all, so what the professor taught used to be very difficult to understand. But, when my teacher heard her play, he immediately noticed that the sound which was produced was fuller and much more intriguing and the effort put in the playing (it was the Rach. D major prelude) was just phenomenal. The torso was inclined at a very sharp angle to the piano and the entire system(shoulders to the fingers) seemed to be involved. But, as my teacher had gone there as a university level student, what the shoulders had to do was not her concern. It was more a sort of a critical analysis of the piece than the technique!
So, my teacher then went to the Central Music School, got permission to just sit and watch the teachers there teach youngsters the technique and then came up with the following conclusions:
1. Even in the simplest of pieces, the entire body HAS to be involved! It produces a great difference even on a piece as easy as the G major menuet by Bach.
2. This automatically results in excellent phrasing, the crescendos seem to have a very natural and seemingly obvious accelerando, and the music seems to have a sparkle and life that you won't get otherwise.
3. Now, also, he learnt that the convenience of the piano can be its biggest disadvantage. Comparing it with a violin, for instance, the violinist would after every phrase have to shift the bow back in order to continue, giving the effect that the music is breathing. The same being not necessary on the piano(All the notes are in front of you), the breathing part is often neglected and the music becomes dead and mechanical.
4. Coming to the term I used in my previous post , ''intonatsiia"; it is actually the russian equivalent of intonation, but has a much wider meaning than what you would normally imagine. You have to create tension and excitement BETWEEN notes! This is the highlight of intonatsiia. Distinguish larger intervals from smaller ones by slightly greater delays. Long notes should always be approached with a delay. A very good example is the middle section of the G minor prelude of Rachmaninov. In the very beginning of this section, the fourth chord in the right hand(CDF#C) and all similar ones, should be approached with a delay i.e. between the one before it and itself! The same is to be applied everywhere, not only Rach, but also Bach, Mozart and literally everything. Its just that in Bach and Mozart, you have to be a little more selective.
Points 1-3 are NOT taught in conservatories. Children there get it by seeing their teachers play. They, when they grow up and become concert pianists won't be able to explain why they do it, its just there! But, such was not the case with my teacher as he had to study it like science!
In conclusion my hint is that, if you follow all what is above, even the simplest piece you play will require a lot of effort, and you will look BUSY while playing, but the result is phenomenal! Also, remember that the worst complement you can get is "What EFFORTLESS playing!". Effortless playing might have the accuracy, but it will NOT convey the emotions, it will be flat and bland! After all, there is much more to piano playing than just speed, accuracy and bravura!!!!!