I am having trouble sourcing this. I sometimes see it referred to as "(Offertorium)" which would indicate that it's from an Offertorium, and this morning found a reference to it being a motet, in which case it's a separate entity altogether.
The original scoring, which is what I'm looking for, is voice (again, I sometimes see soprano, and others mezzo-soprano), C clarinet, 2 violins, viola, cello, and basso.
Is this from one of his Requiems or is it something else, and would anyone be able to upload it, if it is separate? Thanks.