Now this is lovely. Here are the Monks and Choirs of Kiev Pechersk Lavra, with:

…26 hymns from the ancient church, sung by the monks of the historic Kiev-Pechersk cave monastery. Included are rare sacred music pieces by both Rachmaninov and the Italian composer J.Sarti, who was so enraptured by Orthodox singing that he left Italy for Russia in 1724 and lived there the rest of his life. Gorgeously layered, these venerable hymns bring together Byzantine traditions with those of old Russia.

(This post used to link to magnatune.com, where you were able to listen to, or purchase, the album. But that page on magnatune.com is gone, so I’ve removed the links.)