Recently, I attended a workshop discussing the skills needed to become a better accompanist. At the beginning of the session, the clinician stated that the difference between a pianist and an accompanist was the accompanist's awareness of breathing. I was disgruntled by the statement immediately, but tried to give the speaker the benefit of the doubt. As she continued her presentation, I became more and more convinced that she was a total hack who should never speak publicly about the art of piano collaboration. It also set me on my personal development of workshops on this topic about which I am extremely passionate.
I do not consider myself an accompanist. I am a pianist. End of statement. When one accompanies another person on a journey, the implication is that they are simply along for the ride. They are not significantly contributing in the efforts that will lead to the final destination. The same connotation is often held by those who view the pianist as nothing more than an "accompanist." The pianist is not viewed as a contributing member of the ensemble. While the piano part may be simple at times, there are still significant artistic choices that must be made. In my mind, an "accompanist" is someone who merely plays the notes on the page; a pianist brings artistry to the performance, allowing the notes on the page to take on a life of their own.
The distinction moves beyond the use of terminology though. To say that a pianist lacks awareness of breathing displays a total lack of understanding of the careful study of piano performance. Just as singers and instrumentalists rely on the breath to carefully shape their phrases, the pianist must allow the melody to breathe as it rises and falls. Although our instrument is not powered by the flow of air, playing without allowing the music to breathe in a natural way results in a performance that is stilted and lifeless.
Perhaps a better distinction to notice is the difference between a solo artist and a chamber musician. The solo pianist is concerned solely with the sounds coming from his instrument. The chamber pianist, on the other hand, fully understands the necessity of collaborating with another musician -- whether a vocalist, conductor, or instrumentalist -- to achieve a moving musical experience. (Hence the term frequently used to describe this specialized field of playing -- collaborative piano.) Many pianists find themselves living in both worlds at various times. Personally, I believe that pianists tend to prefer performing as a soloist or a collaborative pianist; there seems to be an affinity for one type of playing over the other. Neither pianist is superior to the other; the two simply have different approaches to making music and will often find themselves called upon to perform in the other vein of piano performance. The ultimate goal of both pianists, however, is always the same -- to create the most beautiful sounds possible with the skills they have developed over years of study of the piano.