Last Thursday I had the honor to perform with both of Wayland's major choral ensembles in our fall choral concert. There really is nothing like a great choir concert - powerful text enhanced by wonderful music. Not that everything was profound and moving, you understand...International Choir's performance of Sam Pottle's "Jabberwocky" was, well, frabjous.
You may wonder why a professional pianist might enjoy spending time accompanying choral ensembles. I think there are several direct benefits on both sides here. For my part, I get to directly experience a wide variety of musical styles across more than 500 years of history. Since the piano only goes back 300 years or so (I am of course over-generalizing for the purpose of this post), I would otherwise miss out on an entire period of masterworks.
Also, nothing portrays the integrity of musical line like the human voice. All we instrumentalists can do is approximate its capacity for legato and direct connection to the soul. Every pianist needs choral experience to give him or her the personal experience of creating a totally organic musical line - this has huge implications for how one approaches phrasing and legato on the keyboard. Not coincidentally, I'm a huge proponent of vocal accompanying for this same reason.
For the choir and their director, it is a great benefit to have a collaborator who has the technical facility and musical maturity to become a co-teacher with the conductor. A skilled pianist can illustrate appropriate phrasing, dynamic shifts, breaths, etc., thereby saving many valuable minutes of rehearsal time for the conductor.
Finally, I see a powerful metaphor in the choral experience for productive life in society - how you show up on time (or not), prepare for rehearsal (or not), and interact with your colleagues reflects on your vision for society. Is it all about you, or are you constantly striving to work with others and subordinate your own preferences and inclinations to the leadership of a respected, qualified figure for the greater good? Sounds a bit cheesy, but I really think there's a lot of truth in that.