Stick Time: Challenging Tuning

Tuning. It's a minute-by-minute challenge, isn't it? Some selections sound as though they shouild be easy to sing in tune, but they reveal themselve to be quite difficult.  Then there are works that are almost relentless in the demands on the singers.  Here we listen to an example of a work that requires tremendous tuning discipline (and I think the needed focus is obvious on the faces of the singers).  Study this from the perspective of tuning.