Can anyone recommend some bands (or just tracks) they truly like and which make use of polyphony in vocals or chants. I'm not talking about diphonic throat singing here, but rather of several singing voices superimposing (could be from several singers, or a single singer sampling of his own voice to create the polyphony), such as in these two examples:
Voices is the sixth album by English singer-songwriter Claire Hamill, released in 1986. The title refers to the fact that the album's mostly-instrumental music is entirely a capella, created by sampling and multi-tracking Hamill's voice.
Or you could dive into Sheila Chandra - Weaving My Ancestors' Voices as an introduction. Not much pure vocal layering though, just solo and lovely deep harmonies with the harmonium.
Edit: I also like this one with a wide range of powerful vocals taking the center stage: Lustmord - The Word As Power. Play that on a decent setup.