To understand the Degree of Difficulty inherent in the Nova Singers' season-opening concert, first imagine singing a particular vocal line - be it soprano, alto, tenor, or bass - against the three other vocal lines, and doing it a cappella, to boot.
Then imagine singing your part while those four parts turn into eight.
Then imagine singing your part while those eight parts turn into 12.
And then, imagine staying on your part with 81 people around you attempting the exact same thing.