Musicians understand the importance of regular practice in order to master their craft. We acknowledge that performance is necessary to communicate our thoughts through sound. We agree that it is necessary to read about composers in order to develop a fuller understanding of their music. Sometimes, however, we tend to forget about another valuable part of our development: listening.
Listening allows the developing musician to become acquainted with the repertoire. A pianist may spend his entire life learning new repertoire. Despite his best efforts, there will be no way that he will play all of the solo sonatas written for the piano. When we begin to consider the miniature pieces, concertos, and chamber works written for the instrument, the list of available music becomes daunting. Listening allows us to become aware of repertoire that we may never play, providing a backdrop of the sounds of a composer's works as well as historical eras.
Pianists should also listen to works not written for piano. In order to play "orchestrally" when such a sound is desired, the pianist must be intimately aware of what the orchestra sounds like in all of its colors and varieties. Lyrical, legato lines seem to float from the keyboard with greater ease when compared to the way that a flute or singer might approach the line. A Baroque fugue takes on new life when envisioned as something written for string quartet.
Examining various recordings of a single piece aids the listener in understanding the difference that subtle nuances can make. Additionally, encountering numerous artists sharpens one's ears as they develop their own artistic voice. By considering how different performers shape a single phrase, the pianist is challenged to pursue greater personal artistry while developing their own interpretive voice. With the addition of video performances, the developing musician is able to examine some technical aspects of different pianists. Perhaps a lower wrist placement seems to be associated with a greater warmth of sound. Another video might suggest an unusual fingering pattern. These observations combined with the sound produced can be taken to a practice room for careful experimentation.
Lastly, listening develops the musical taste of the pianist. While I tend to enjoy listening to specific players, it is important to listen to others as well. I learn from hearing what I don't particularly like as much as I do from what I most enjoy. It is an interesting exercise to ask others for suggestions -- peers, teachers, and non-pianists -- of recordings that they enjoy and find interesting. You'll find that you are exposed to approaches you did not expect and might find something new to appreciate.