Playing the piano is like being every member of an orchestra whilst at the same time conducting it. The pianist is responsible for all aspects of the performance, from the large-scale structural shaping of a piece to the smallest detail of accompanying figuration. In preparing a score they need, therefore, to engage with it on many different levels. Like the orchestral players, they have to diligently practice the passagework; but they must also live and breathe the score as a conductor does—forging, somehow, their own interpretation. A convincing performance must have command of both these aspects, as well as everything in between.
A lot of the pleasure of practising stems from the fact there are so many ways to think about the piece you’re learning. It’s not just about endlessly repeating the hardest bits; properly practising a piece is like being an explorer. Experimenting with alternatives of articulation, phrasing, dynamics, pedalling, balancing, tempo, rubato etc. is how you discover the musical possibilities in a work and your own feelings on the piece. It is also useful to experiment away from the piano (i.e. in your head whilst you walk to the tube, or something), where technical difficulties cannot hamper inventiveness: the challenge then is to recreate these imaginings at the piano. In searching for different sounds and meanings you discover things about the music, the composer, the piano, and even yourself. The beauty of all this is that everyone comes up with something different.
Once you’ve practised a piece so much it’s become ‘internalised’, you become completely free and can discover new things in it every time you play. In the best performances you find new nuances and ways to interpret phrases—which might be quite different from any of the ways you’d practised them—on the spur of the moment, in front of the audience. This is a big part of the excitement of live performance, from the point of view of the performer as well as the spectators. Practice should be the preparation for this moment: exploring as many possibilities as you can think of so that a plethora of ideas are at your disposal in performance, and becoming so well-acquainted with the score that you can re-manipulate it in any way in response to a flash of inspiration. All that then remains is to forget all this hard work by letting go on stage and seeing what comes out!
