They sang the whole of Gesualdo's wonderful Tenebrae: dark, gnarly, full of lamentation. I've got to get the CD of this!
If you are intrigued, here's my review from Cleveland Classical.
Here's one clip I found on YouTube.
Listen to the strange patter of rain on the roof at 0:32 "viri justi tolluntur" (the just people are taken away; and no one notices). And the modulation at 1:04..."et erit in pace": the memory of the just will be in peace.