Besides being excellent vocalists and musicians, choral singers have to be great team players.
Everyone has to know his or her strengths and weaknesses (and self-knowledge can be so elusive!), and contribute accordingly. In performance, some lead in providing impeccable pitch or rhythm, others by offering an unfailingly lovely timber, still others by reliably delivering the highest or lowest notes as needed.
But a great choir needs to rehearse well together, too. So in addition to all those audible skills above, a successful choir relies upon those especially astute musicians who model just the ideal phrasing or articulation, or ask just the right (leading) question to help the process along. And upon some who exude enjoyment and serenity, which is contagious. Some find the perfect opportunity to crack a joke. And MOST need to exhibit good-natured patience as, say--for a random example--the basses struggle to find a pitch, or perhaps the conductor makes a confusing gesture or chooses the wrong tempo (AGAIN!).
It's just like anything else--when people work together, they can make something beautiful AND have a lot of fun.