Chi no Hibiki - Higashi Yuroppa wo Utau by
Geinoh Yamashirogumi
may already be well known but I love this group. this is their take on (mostly) polyphonic Eastern European choral singing. No other instruments required or needed.
My mum used to make a traditional Ukrainian meal for Christmas and would take us to bless the food at the Orthodox church. It was a brilliant church and this album is reasonably similar to the chorus sections they had there. I woudnt categorize myself as religious, but I'm fascinated by the music it's produced