The fact (good) death metal/black metal bands can conjure such an impacting voice warrants credit right of the bat.
Taking the human voice beyond 'la de da' and 'ohhHHOHhoHOHohHOH' isn't some living room event.

I realize that many people arn't patient enough to listen attentivley and gather the magic behind the mayhem...
Listen to 'zombie inc' from In Flames... really listen..
theres THOUGHT behind the voice..not just some mindless twisting of pitch or display of 'oooooohhhh's and 'ahhhhhhhh's.

the same goes for 'Demon in viens' and 'Aardvark Trail' from soilwork.Death's '1000 eyes'.Lamb of god's 'Vigil'.
Also almost anything by carcass.

eh whatever... music is to diverse to say 'this is this and that is that'.