Mozart Requiem? No, we’re not performing that, we’re performing the Schubert Mass no. 2 in G Major. And a beautiful piece it is, too. The opening Kyrie, at least, sounds very familiar and I wonder if we might have performed it before. However, I don’t think we’ve done the whole thing.
All the usual Web resources are available. There’s an interesting article on Wikipedia. A Youtube search turns some good videos, including this one. (That’s a high men:women ratio, isn’t it? Don’t the tenors sound great!) There’s a good set of MIDI files on Cyberbass. Incidentally, I find that Cyberbass works OK for me with Internet Explorer and Chrome; with Firefox, the music plays, but I can’t see the little control bar for the player.