I saw these guys perform yesterday: the Moscow Patriarchate Choir. I like religious music in languages I don't understand: I can ignore the content and fall into the music. It was an amazing performance: 12 unamplified men in a massive hall. They're perfect musicians, and their voices are astonishingly loud, clear and varied. The bass singers have to be heard to be believed. I also really enjoyed their group dynamics. Despite looking pretty severe, they could be seen appreciating each others' solos.
The theme of the evening was the Orthodox Christmas music. The audience, however, were rather closer to death than birth - one poor old man keeled over a few feet from me. Death seems to attend classical concerts quite regularly: always good pickings.