...and it occurs to me that we have a similar example in Anglo-American culture, due to the sacralization of military ceremony: nobody accompanies songs with the bugle. The reason being that the solo bugle has the status of a holy instrument in military-religious ceremonies like those that commemorate dead soldiers, so people don't join in and sing along with the Last Post.

It's not that their voices are considered sacred, it's that compared to what is effectively the incarnate voice of the God of War speaking from his throne in the cenotaphs, they aren't.