I think it takes a lot of preparation to be truly spontaneous.
Either way, it has to be unique and fresh each time, or I get bored.
Why should one work over several hours per day on a specific way to play a piece, just to ignore it when actually performing?
Preparation, beeing the process of preparing something, in this case, a piece of music, i guess is not only about which notes to play, but also how to play them. As the interpreter makes decisions on how to perform a piece, the less liberties he will have while performing (because he decided upon a certain way). So if study consists of this kind of work, then, the more you study, the less liberties you will have while performing.
Preparation, beeing the process of preparing something, in this case, a piece of music, i guess is not only about which notes to play, but also how to play them. As the interpreter makes decisions on how to perform a piece, the less liberties he will have while performing (because he decided upon a certain way). So if study consists of this kind of work, then, the more you study, the less liberties you will have while performing. Why should one work over several hours per day on a specific way to play a piece, just to ignore it when actually performing?
But it depends also of the different composers: Chopin, Liszt versus JS Bach, for example...
Can you name a pianist for each approach? It would be interesting to have some audio or youtube examples of that.