Excellent topic!

There are many kinds of mental practice, which aim at different areas. Many pianists integrate all these areas and aims and come up with complex mental routines. Perhaps the most famous example is Glenn Gould, mostly because he took great pains to explain it all. Check it out:
- “These days and throughout my professional life, indeed, I’ve practised only on an if-, as- and when-needed basis, and only for the purpose of consolidating a conception of a score - never for the sake of contact with the instrument per se. I’ll give you an example. The most recent recording I’ve made as of the date of this interview is the Brahms Op. 10 the four ballades. I recorded them three weeks ago in New York. It happens that I’d never played them before - not even sight-read them – […] I’d never even heard them played until I decided to record them.
[…] for approximately the next six weeks I studied the score from time to time, and developed a very clear conception of how I wanted to approach the ballades.[…] But as for playing them, I spent only the last two weeks at the keyboard and […] it averaged about one hour a day. […] that one hour gave me he opportunity to play through the ballades twice on each occasion (they’re almost exactly half an hour in length) and think about the conceptual changes I wanted to make.
Now, those conceptual changes were reinforced, needless to say, by running the ballades through in my head many dozens of times when driving along in the car or conducting them in my studio. […]
- But this presupposes that one has a very specific and very secure conception of what is involved in playing the piano.
- Oh, absolutely. It presupposes that at some point, one has hit upon precisely the co-ordinates that are involved and then frozen them, stored them in such a way that one can summon them at any time. What it all comes down to is that one does not play the piano with one’s fingers; one plays the piano with one’s mind. If you have a clear image of what you want to do, there’s no reason it should ever need reinforcement. If you don’t, all the fine Czerny studies and Hanon exercises in the world aren’t going to help you.”
(These are a few excepts, you can read the full interview in David Dubal: The World of the Concert Pianist).
Trying to do what Glenn Gould does however is not the best approach, since his is a completely integrated approach polished over many decades. If this is all new to you, the best thing is to break down the process into much more limited aims and strategies:
- Memorise the piece away from the piano. (Check Walter Gieseking & Karl Leimer’s book “Piano Technique” where this is explained in detail).
- Study the score and analyse it away from the piano.
- Read the score and “hear” the music in your mind.
- Practise in your mind (by visualising your self practising – then mentally feeling the touch sensations involved and mentally hearing the music produced. The beauty of this kind of mental practice is that you can play perfectly! But beware, when done properly this is really tiring, so do not overdo it.)
The main difficulty with mental practice is that people tend to delude themselves they are doing it, when they are in fact just daydreaming about it. For instance, truly effective mental practice must be done in real time, that is, if it takes you ten minutes to go through a Beethoven Sonata at the piano, real mental playing should take the same time. This is one of the times where a metronome could be invaluable, by making sure you are not fast-forwarding.
Best wishes,
Bernhard.